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TEXT-BOOK 



ON 



CHEMISTRY. 



FOR THE USE OF 



SCHOOLS AND COLLEGES. 



/ BY 

/ 

HENRY DRAPER, M.D., 

PROFESSOR ADJUNCT OF CHEMISTRY AND NATURAL HISTORY 
IN THE UNIVERSITY OF NEW YORK. 



Witb more tfjati gjree JguutrreU JHlustrattons* 



NEW YORK: 

HARPER & BROTHERS, PUBLISHERS, 

FRANKLIN SQUARE. 

1 8G6. 



Entered, according to Act of Congress, in the year one thousand 
eight hundred and sixty -six, by 

HARPER & BROTHERS, 

In the Clerk's Office of the District Court of the Southern District 
of New York. 



o 



PREFACE, 



This text-book on Chemistry is intended for the use 
of Schools and Colleges. It embodies the valuable 
parts of the work on the same subject published by my 
father in 1846, which satisfied so completely the public 
wants that it passed thrqugh more than forty editions. 
It has been found necessary to make this book larger 
than that by a hundred pages, and to incorporate a very 
considerable number of new illustrations, in order to 
bring the subject fully up to the present time. A free 
use has been made of all the most recent authorities, 
both in English and other languages, and it is believed 
that nothing essential for the student has been omitted. 
The form the book has taken has been determined by 
long experience in teaching, not only at the University, 
but als.o in the many Colleges and Schools where the 
former text-book has been and is used. The subject is 
presented in the most practical way, all needless techni- 
calities are avoided, and the facts are stated in plain 
language suited to the class-room. 

At the bottom of each page a series of questions will 
be found ; they are intended to assist a teacher in point- 
ing out the more essential facts. The copiousness of 
illustration will also prove to be of material advantage 
in schools where there is a deficiency of apparatus for 
experiment. 

Henry Draper, M.D. 

University of New York, 1868. 



CONTENTS. 



Lecture Page 

L History of Chemistry 1 

II. History of Chemistry 7 

III. Heat 11 

IV. Expansion of Gases and Liquids 15 

V. Expansion of Liquids and Solids 22 

VI. Expansion of Solids 27 

VII. Specific Heat of Bodies 31 

VIII. Specific Heat and Latent Heat 36 

IX. Latent Heat s 42 

X. Vaporization 47 

XI. Ebullition 53 

XII. Vaporization 58 

XIII. Evaporation and Interstitial Radiation 65 

XIV. Conduction 72 

XV. Radiation 76 

XVI. Theory of the Exchanges of Heat... 83 

XVII. Of Light 87 

XVIII. The Constitution of Solar Light ; 93 

XIX. Wave Theory of Light 100 

XX. Wave Theory of Light 103 

XXI. Wave Theory of Light 107 

XXII. Production of Light Ill 

XXIII. Chemical Action of Light 116 

XXIV. Photography 119 

XXV. Electricity 124 

XXVI. Theory of Electrical Induction 129 

XXVII. Laws of the Distribution of Electricity and Theo- 
ries of Electricity 133 

XXVIII. Electrical Induction and Faraday's Theory 138 

XXIX. Voltaic Electricity , ." 147 

XXX. Forms of the Voltaic Battery 150 

XXXI. The Electro-Chemical Theory 157 

XXXII. Ohm's Theory of the Voltaic Pile 165 

XXXIII. Electro-Dynamics ; 178 

XXXIV. The Nomenclature 191 

XXXV. The Symbols 195 

XXXVI. The Laws of Combination 199 

XXXVII. Constitution of Bodies 204 

XXXVIII. Chemical Affinity... 212 

XXXIX. Pneumatic Chemistry — Oxygen 218 

XL. Oxygen — continued 224 

XLI. Hydrogen 22!) 

XLII. Water 234 

XLIII. Nitrogen — Atmospheric Air 241 

XLIV. Atmospheric Air 247 



Vlll 



CONTENTS. 



Lecture . Page 

XLV. Atmospheric Air .253 

XL VI. Compounds of Nitrogen and Oxygen. 258 

XLVII. Compounds of Nitrogen and Oxvgen 261 

XL VIII. Sulphur 265 

XLIX. Compounds of Sulphur and Oxygen 269 

L. Sulphur — Phosphorus 271 

LI. Compounds of Phosphorus and Oxygen — Chlorine 275 

LIL Chlorine 280 

LIII. Chlorine— Iodine 1 284 

LIV. Bromine— Fluorine— Carbon 289 

LV. Carbonic Acid . 295 

LVI. Cyanogen — Boron— Silicon — Ammonium 300 

L VII. Chemical Properties of the Metals. 309 

LVIII. Potassium 313 

LIX. Sodium — Lithium — Caesium — Rubidium — Ba- 
rium .* 319 

LX. Strontium — Calcium — Magnesium, etc 326 

LXI. Manganese— Iron 338 

LXII. Iron— Nickel— Cobalt— Zinc 343 

LXIII. Cadmium — Tin — Chromium, etc 349 

LXIV. Arsenic 355 

LXV. Arsenic — Antimony — Tellurium — Copper 359 

LXVI. Lead— Bismuth— Silver 365 

LXVII. Mercury — Gold— Palladium — Platinum, etc 371 

LXVIII. Organic Chemistry 377 

LXIX. Analysis of Organic Substances 384 

LXX. The Non-Nitrogenized Bodies..." ! 391 

LXXI. Action of Agents on the Starch Group 397 

LXXII. Metamorphoses of the Starch Group by Nitrogen- 

ized Ferments 402 

LXXIII. The Derivatives of the Fermentative Processes... 407 

LXXIV. Derivative Bodies of Alcohol 413 

LXXV. Oxidation of Alcohol 417 

LXXVI. Derivatives of Acetyle — The Kakodvle Group 422 

LXXVII. The Wood-Spirit Group 426 

LXXVIII. The Potato-Oil Group— The Benzoyle Group 430 

LXXIX. The Salicyle and Cinnamyle Groups 435 

LXXX. The Nitrogenized Principles 439 

LXXXI. Bodies allied to Cyanogen 445 

LXXXII. Mellone— Urea 449 

LXXXIII. The Vegetable Acids , 453 

LXXXIV. The Vegetable Alkaloids... 458 

LXXXV. The Coloring Bodies 465 

LXXXVI. The Fatty Bodies 469 

LXXXVII. The Resins, Balsams, and Bodies arising in De- 
structive Distillation. 474 

LXXXVIII. Animal Chemistry 4S0 

LXXXIX. Origin and Destiny of the Fats and Neutral Nitro- 
genized Bodies 483 

XC. Introduction and Transmission of Food through 

the System ; 487 

XCI. Nature of Respiration and Secretion 490 



INTRODUCTION, 



LECTURE I. 

History of Chemistry. — Chemistry the Science of 
Analysis and Synthesis. — Its early History. — Alche- 
my. — The Philosopher* s Stone. — The Elixir of Life. 
■ — Discovery of the strong Acids. — The second Stage 
of Chemistry. — Cause of the Union of Bodies. — 
Doctrine of Acids and Alkalies. — Affinity. — The 
Electro- Chemical Theory. — Dalton's Atomic Theory. 
— Atoms and Interstices. — Atoms attracted together 
by Cohesion and repelled by Heat. — Experimental 
Illustrations. 

Chemistry may be defined as the Science of Analysis 
and Synthesis. It deals with the atoms of which bod- 
ies are composed, and investigates the changes of form 
and properties they suffer by decompositions and com- 
binations. It leaves to Natural Philosophy the de- 
scription of the action of masses of matter upon one an- 
other. 

Chemistry has existed from the earliest times, having 
been brought into Europe from the East. At first con- 
sisting of a few isolated facts, w^hich, as their number 
increased, were grouped together by the aid of various 
hypotheses, it has in recent times acquired precision, and 
come to be regarded as one of the exact sciences. The 
great progress which it made in the Middle Ages was 
due to the impression then existing, that by its aid men 
might discover the means of transmuting the baser into 
the nobler metals, might learn how to turn lead into 
gold. The desire of acquiring wealth suddenly was the 
moving spring that tempted many to waste their entire 
possessions in long-continued experiments. Alchemy, 

What are the objects of chemistry ? What does Natural Philoso- 
phy treat of? What is the early history of chemistry? What is 
meant by Alchemy ? 

A 



2 HISTORY OF CHEMISTRY. 

the Chemistry, the art of making the precious metals, 
as the science was termed by the Arabians, pursued an- 
other equally unattainable end, the search ftrr the Elixir 
of Life, by which existence might be indefinitely pro- 
longed. The alchemists supposed, as gold was the no- 
blest of the metals, that if it could be obtained in a dis- 
solved condition, potable gold, the problem would be • 
solved. 

In the prosecution of such investigations, conducted 
by many persons, and with the utmost ardor, great 
facts could not fail to be continually found out, facts 
which form the solid basis of modern chemistry. Of 
these, the most important was the discovery of the 
strong acids. Nitric acid was procured by Djafar, or 
Geber, toward the end of the eighth century, by distil- 
ling Cyprus vitriol, alum, and saltpetre together ; and 
aqua regia was formed by the addition of sal ammoniac 
to that acid. In the ninth century, Rhazes described 
sulphuric acid, having prepared it by the distillation of 
green vitriol ; he also obtained absolute alcohol by the 
action of quick-lime on spirit of wine. 

When we recollect that previous to this time vinegar 
was the strongest acid known, it will be at once per- 
ceived how greatly the powers of the chemist were in- 
creased. He could decompose substances which had 
hitherto proved entirely intractable, and could form a 
large number of new compounds. 

The discovery of aqua regia, the solvent for gold, by 
Geber, and the soon-proved inefficacy of potable gold to 
prolong life, gave a death-blow* to that phase of alche- 
my. The transmutation of metals is still sought for, 
because no demonstration of its impossibility has been 
offered. Indeed, the mass of evidence looks the other 
way, and many eminent chemists are willing to admit 
that it may at any time be accomplished. The pursuit 
of the elixir of life ended in the introduction of chemis- 
try into medicine, Basil Valentine publishing a treatise 
on the virtues of antimony in the fifteenth century, and 
Paracelsus introducing mercury as a specific in certain 

Wkat is the Elixir of Life? What great facts were discovered by 
the alchemists ? Why was the discovery of the acids important ? 
What is potable gold, and its use? Is transmutation of the metals 
possible ? 



HISTORY OF CHEMISTRY. 3 

affections in the sixteenth. Van Helinont, who first 
used the term gases, was the last alchemist of any note. 

The second stage in the progress of chemistry may be 
regarded as originating in attempts to investigate the 
reason of the union of bodies. Alchemy left a mass of 
facts without order or arrangement, having no connec- 
tion with one another. Sylvius, a Dutch physician, 
born in 1614, was the author of the doctrine of acids and 
alkalies, and their neutralization, his leading idea being 
that for substances to enter into union they must pos- 
sess opposite, and not similar qualities. He showed that 
a compound may differ altogether in properties from 
the bodies from which it has been formed : thus, sul- 
phuric acid, a sour, corrosive liquid, uniting with lime, 
a caustic solid, produces sulphate of lime, an inert body. 

This doctrine of the affinity of substances of opposite 
natures was developed by Geoffroy,. who constructed 
tables showing the graduated or elective affinity of bod- 
ies for one another, some exhibiting a weaker and oth- 
ers a stronger disposition to unite with a given sub- 
stance. These tables, which are even now of considera- 
ble use, do not, however, represent the order of affinity, 
but only of decomposition, on account of the interfer- 
ence of certain external agents, such as temperature, 
solubility, cohesion. 

Eventually, it was stated by Davy, in his electro- 
chemical theory, that the condition determining the 
union of bodies is that they must be in opposite electri- 
cal conditions. Thus, for example, potash is composed 
of potassium, an electro-positive metal, and oxygen, an 
electro-negative gas. On this theory, all bodies belong 
to one of two groups, electro-positive or §Jectro-nega- 
tive, depending on w T hich pole they pass to when com- 
pounds containing them are decomposed by a voltaic 
current. Chemical affinity is therefore an electrical phe- 
nomenon. Although apparently simple, difficulties of a 
formidable kind present themselves to this hypothesis. 
The doctrine has received its utmost development by 
the researches of Faraday, to be described hereafter. 

What was the second stage of chemistry? What is the doctrine 
of acids and alkalies ? What are Geoffroy's tables ? What do they 
indicate? What does the electro-chemical theory affirm? What 
two groups are bodies divided into ? 



HISTORY OF CHEMISTRY. 



Fig. 1. 



Dalton's atomic theory accounts for the union of bod- 
ies in definite proportions by supposing that they con- 
sist of atoms, or indivisible portions, and that in the 
case of each substanee the atom has a definite and spe- 
cial weight. Thus, the hydrogen atom being taken as 
the unit, the atom of oxygen is eight times as heavy, 
that of sulphur sixteen, that of gold a hundred and 
ninety-seven. The weight of an atom of water, consist- 
ing of one of hydrogen and one of oxygen, must be nine, 
and can not be either more or less. In the case of sub- 
stances combining to form more than one compound, 
the proportions found in the various compounds bear a 
simple relation ; thus, an atom of carbon weighing six 
may combine with one of oxygen weighing eight to 
form carbonic oxide, or with two of oxygen, weighing 
sixteen, to form carbonic acid, but no intermediate pro- 
portions are possible. 

The atoms of which bodies consist are not in contact, 
but are separated by interstices, or 
intervals. The distance by which 
they are separated admits of 
change by external agents. If, for 
example, a metallic ball, Fig. 1, be 
so adjusted to a ring that, when 
cold, it will just pass through it, 
on subjecting the ball to heat it 
will be found to have dilated, and 
will no longer pass through, but 
will remain sustained. On allow- 
ing it to cool in that position, it 
contracts again to its former size, 
and will fall through the ring spon- 
taneously. The heat has in this 
case partially overcome the mutu- 
al attraction of the atoms composing the metal ; they 
have receded from one another, and an enlargement is 
the result. As the heat in the latter part of the exper- 
iment radiates away, cohesion again draws the atoms 
together to their original distance. 

What does the atomic theory affirm ? What is the weight of an 
atom of hydrogen ? of oxygen ? of water ? How are atoms sepa- 
rated? Describe the apparatus Fig. 1. What was the effect of the 
heat ? 




HISTORY OF CHEMISTRY. 




By the influence of pressure Ave may Fi '&- 2 - 

demonstrate the same fact, that atoms 
are separated by variable intervals. Let 
a glass tube, a b c, Fig. 2, bent as repre- 
sented, be partly filled with water. On 
exerting pressure by the aid of the pis- 
ton c, the column of air in a b may be 
made to diminish in size. The atoms 
of which the air consists have approached 
one another, and the size of the inter- 
vening interstices has been lessened. 

Heat exercises a similar effect in the 
case of gases to that exhibited in solids. 
This is shown by the apparatus Fig. 3, in which a is a 
glass bulb terminating in a tube, 5, dip- Fig. 3. 

ping below the surface of some water in 
a vessel, c. On warming the bulb a by 
the hand, the liquid originally standing 
at the point b descends, indicating that 
the air in a has expanded. Its atoms 
have been forced apart by the heat. 

By decreasing the pressure exerted by 
the atmosphere we may also cause an in- 
crease in the size of the interstices of a 
substance. In Fig. 4, a is a glass globe 
nearly -filled with water, but containing a bubble of air 
at the upper part. Its neck, 5, descends, 
air-tight, through the top of a bell-jar, d^ 
and terminates in a vessel of water, c. 
On exhausting the air from the bell-jar 
by the air-pump, the bubble of air, a, 
will be seen to expand, and will eventu- 
ally fill the entire bulb and tube. On 
restoring the pressure of the air, the bub- 
ble contracts to its former size. 

An illustration of cohesion, the force 
that opposes heat in the regulation of in- 
terstices, is seen in the experiment of the 
bullets. If two leaden bullets have each 
a bright spot pared upon it, and the two be then pressed 

Describe Fig. 2. What fact does Fig. 3 illustrate? How may the 
interstices between atoms be enlarged ? Describe Fig. 4. Describe 
the experiment of the leaden bullets. 




Fig. 4. 




HISTORY OF CHEMISTRY. 



closely together, they cohere, and can only be parted 
by the exertion of considerable force. 

The distance through which these forces, attraction 
and repulsion, act, is very minute ; for if, in the above 
experiment, the bullets be separated by the smallest in- 
terval, no attraction ensues ; they must be forced to- 



Fig. 5. 



g ether till less than a millionth 




of an inch intervenes, as was 
shown by Newton. The same 
fact is proved by the apparatus 
Fig. 5, which consists of a plate 
of glass, a, supported over some 
mercury in a cup, e. To the 
other arm of the balance, b c, is 
hung a pan, <?, containing weights. As long as the 
glass and mercury are not in contact no attraction is 
exhibited, but immediately they touch a considerable 
weight must be put into d to draw them apart. 

The atomic theory forms the foundation of modern 
chemistry, and is applicable not only to the combina- 
tion of elements, but also to combinations of their com- 
pounds. As we shall see in organic chemistry, there 
are bodies which act like elements whose atoms or mole- 
cules are exceedingly complex, containing several ele- 
ments and many atoms of each. 



Through what distances do attraction and repulsion act ? De- 
scribe Fig. 5. What is the present position of the atomic theory ? 



HISTORY OF CHEMISTRY. 



LECTURE II. 

History of Chemistry. — The third Stage of Chemis- 
try, — Investigation of the Nature of Bodies. — An- 
cient Doctrines. — The Phlogistic Theory, — Lavoisier 
introduces the Use of the Balance. — The Nomencla- 
ture and Symbols. — The fourth Stage. — Assertion of 
the Indestructibility of Matter. — Correlation and 
Conservation of Force. — Illustrations of Converti- 
bility of Force. — Atoms regarded as Centres of 
Force. 

At the same time that the investigations terminating 
in the atomic and electro-chemical theories were being 
carried on, the third stage of chemistry, the examina- 
tion of the nature of bodies, was in progress. 

In ancient times it was supposed that there were four 
elements, earth, air, fire, and water, and that from them 
arose all known substances. The alchemists introduced 
as a substitute the doctrine that the three components 
of all bodies were salt, sulphur, and mercury, and that 
their difference of properties arose from variation in the 
proportions. Hence transmutation was possible. To 
these elements Stahl added phlogiston, the principle of 
inflammability, and by its aid chemists were enabled to 
explain all phenomena until the beginning of this cen- 
tury. For example, when metallic earth, or calx, was 
brought into its reguline or metallic form, it was sup- 
posed to have imbibed a certain proportion of phlogis- 
ton. On subjecting the metal to the action of fire, if, 
as in the case of lead, it returned to the earthy condi- 
tion, it was said that the phlogiston had been expelled. 
The reduction of what we now term oxides, by the aid 
of charcoal, was asserted to be due to the fact that char- 
coal contains a large proportion of phlogiston, and read- 
ily imparts it to the metal. The metals were compounds 

What were the four elements of antiquity ? What were the ele- 
ments of the alchemists ? What addition did Stahl make to them ? 
How did he explain the action of fire on metals ? 



8 HISTORY OF CHEMISTRY. 

of calx and phlogiston, the calx or oxide being the sim- 
ple body. 

The phlogiston theory was destroyed by Lavoisier, 
who, by the introduction of the balance into such inqui- 
ries, showed that the metal gains in weight when it 
assumes the earthy appearance under the influence of 
fire and air, and that the air loses as much as the metal 
gains. The advocates of the old theory attempted to 
account for this fact by assuming that phlogiston was a 
principle of levity, and in combination rendered bodies 
lighter. It was regarded as identical with hydrogen, 
or phlogisticated air, as that gas was called. 

With the introduction of the balance, chemistry be- 
came at once an exact science. The proportions in 
which elements combine to form compounds were as- 
certained with precision, and the experiments necessary 
for the completion of the atomic theory, by determining 
.the atomic weights of bodies, were undertaken. An 
element was defined to be a body not decomposable by 
any known agency. 

At the same epoch the defects in the system of nam- 
ing substances were remedied by substituting for the 
old arbitrary titles, such as green vitriol, Epsom salts, a 
new nomenclature, and a language of symbols. Every 
substance was named according to its composition, and 
its constitution clearly expressed by a short formula. 
This improvement is due to a commission of French 
chemists, Lavoisier, De Morveau, Berthollet, and Four- 
croy. Although the present wants of chemistry are 
hardly supplied by this nomenclature, yet it has worked 
its way into the arts, and been so generally adopted, 
that a better successor than any yet proposed will have 
to be found before it can be displaced. 

The last stage through which chemistry has com- 
menced to pass is that asserting the indestructibility of 
matter. In the old time, when a substance, as carbon, 
for example, was exposed to the action of fire and dis- 
appeared from view, it was supposed to have been 
destroyed or dissipated. • At the same period it was 

By whom was the balance introduced into chemistry? What 
consequences ensued ? Why was phlogiston assumed to be a prin- 
ciple of levity ? How was the nomenclature introduced ? What is 
the last stage of chemistry ? 



HISTORY OF CHEMISTRY. 9 

imagined that new bodies could be created from noth- 
ing. 

But the discovery of carbonic acid by Black and ox- 
ygen by Priestley led to another explanation of com- 
bustion, and proved that, although in that operation 
bodies may change their form, their atoms still exist, 
and may be recovered. In the burning of carbon the 
atoms are not destroyed, but only take on a gaseous 
form, and by the action of the leaves of plants, under 
the influence of sunlight, may be brought again into a 
visible condition. If, in a closed flask of air, counter- 
poised on the arm of a balance, a few grains of gun- 
powder be exploded, though the solid has disappeared 
from sight, the contents of the flask weigh as much as 
ever ; that arm of the balance does not move upward. 

To the doctrine of the indestructibility of matter has 
been added that of the correlation and conservation of 
force. By these terms it is implied that force is equal- 
ly indestructible with matter, but that, in addition, it 
may present a variety of transformations. It may be 
stored up, or disappear in a latent state, as in the case 
of heat and light concealed in plants, and originally de- 
rived from the sun. Heat, light, electricity, motion, are 
all regarded as mutually convertible without loss. The 
conversion of motion into heat may be illustrated by 
an experiment. If a piece of metal tube, closed at the 
bottom, be so arranged, Fig. 6, as to be set in rapid rev- 

Fig. 6. 




olution, on filling it with cold water, and causing its 
exterior to be compressed by a pair of hinged pieces of 

How may it be shown that matter is not destructible ? What is 
meant by correlation and conservation of force? Explain the ex- 
periment illustrated in Fig. G. ■ 

A 2 



10 HISTORY OF CHEMISTRY. 

wood, T, the friction will produce in a few minutes heat 
enough to boil the water. If a cork be inserted into 
the mouth of the tube, it will be violently expelled after 
a short interval. 

Many experiments showing these conversions might 
be described. By a thermo-electric pile, heat may 
be converted into a current of electricity, magnetism 
produced in a coil, chemical affinity exhibited in the de- 
composition of solutions, and light given out in the 
spark. 

The doctrine of the conservation of force is by no 
means new, having been asserted by the i^rabians, who 
included the force exhibited in the animal functions, 
even intellection, in the same category. 

In order to obtain a clear idea of the properties of the 
elements it will be first needful to enter somewhat in 
detail into a description of the forces acting upon them 
— heat, light, and electricity. Matter can not exist ex- 
cept under their influence, and they can not manifest 
themselves without it. It must, however, be borne in 
mind that eminent men have been found in ancient 
times, and also at the present epoch, who entirely deny 
the existence of matter ; and, carrying the atomic theo- 
ry one step farther than it is here set forth, assume that 
the so-called atoms are nothing but centres, or foci, of 
force. 

What effects may be produced by a thermo-electric pile? Who 
were the inventors of the doctrine of the conservation of force? 
What are the forces of chemistry ? 



PART I. 

THE FORCES OF CHEMISTRY. 



LECTURE III. 

Heat. — Tico Hypotheses of the Nature of Heat, the 
Material and the Mechanical. — Influence of Heat on 
Inorganic and Organic Substances. — Transference 
and Equilibrium of Heat. — Heat affects the Magni- 
tude of Bodies and their Form. — Affects Measures 
of Time and Space. — Determines the Distribution 
of Animals and Plants. 

There are two hypotheses of the nature of heat, the 
first of which regards it as a material substance, with- 
out weight, having a self-repulsive power, and an at- 
traction for the particles of matter. The second sup- 
poses it to be a result of the vibration or movements of 
the atoms of which bodies are composed, and is termed 
the mechanical theory of heat. It also attempts to in- 
dicate with precision the exact mechanical equivalent 
of heat, expressing it in " foot-pounds," a term signify- 
ing the falling of one pound a foot. Thus it is said that 
the heat necessary to raise a pound of water one degree 
in temperature is equal to 772 foot-pounds. 

So great is the control heat exercises over chemical 
changes that few experiments can be made in which 
transformations take place without disturbance of tem- 
perature, sometimes heat and sometimes cold being pro- 
duced. 

In the organic world, also, heat plays an equally im- 
portant part. Life can only be sustained within a nar- 
row range of temperature, the one hundred and eighty 

How many hypotheses are there of the nature of heat ? Describe 
each. What is the meaning of the term foot-pound ? What quan- 
tity of heat is required to raise a pound of water a degree ? Ex- 
plain the control of heat over the organic world. 



12 



HEAT PRODUCES EXPANSION. 



degrees which intervene between the boiling and freez- 
ing points of water ; and, indeed, the limits are narrower 
than that, for in the higher tribes a very slight varia- 
tion from a fixed degree causes the operations of the 
body to be seriously interfered with, or even stopped 
altogether. 

When an ignited mass, as a red-hot ball, is placed in 
the middle of a room, common observation satisfies us 
that it rapidly loses its heat, its temperature descending 
until it becomes the same as that of the surrounding 
walls and other bodies. This loss is due to several 
causes. A part of the heat is carried aw T ay by contact 
with the stand which supports the ball, a part by cer- 
tain motions established in the surrounding air, and a 
part by radiation. This removal passes under the name 
of transference ; and as soon as the temperature has 
declined to that of the adjacent bodies, an equilibrium 
is said to have been attained. 

There are two methods by which caloric can be 
transferred : 1st. By radiation ; 2d. By convection. 
Of the former we have two varieties — general radiation 
and interstitial radiation. 

Substances, no matter what their form, solid, liquid, 
or gaseous, expand by increase of heat. 
The experiment Fig. 1 shows this fact in 
the case of a metallic ball. That the same 
is true of liquids is proved by taking a 
glass tube, a b. Fig. 7, open at one end, 
but having a bulb blown on the other. 
The bulb and part of the tube to b being 
filled with w r ater or any other liquid, a 
spirit-lamp is to be applied. The fluid 
soon commences to rise in the tube 5, the 
dilatation increasing w r ith the temperature. 
If the tube be emptied of the fluid, and 
inserted, as in Fig. 8, in a glass of water, 
the expansion of gaseous substances can be shown; for, 
on warming the bulb «, the air it contains expands, and 
escapes in bubbles through the water in c. 

Describe the manner in which a red-hot ball cools. Define the 
term transference of heat. Define the term equilibrium of heat. 
By what methods may heat be transferred. Describe Fig. 7. De- 
scribe Fig. 8. 



Fig. 7. 





HEAT AFFECTS MEASURES. 13 

Solids, liquids, and gases expand, F & 8 - a 

therefore, as their temperature rises, 
and contract as it falls. The size of 
all objects is determined by their 
temperature. A measure which is a 
yard long in summer is shorter in 
winter; a vessel which holds a gal- 
lon in winter holds more in summer. 
The appearance of stationary magni- 
tude of such objects is altogether a 
delusion. They change with every 
hour of the day. 

Heat also determines the form of bodies ; that is, 
whether they shall be solid, liquid, or gaseous. A mass 
of ice raised to 32° melts into water, a liquid; and if 
the water be heated to 212° it turns into steam, a gas. 
The water is thus made to exhibit all the forms of mat- 
ter by change of temperature. 

In the same manner that it affects our measures of 
space, heat affects our measures of time. Clocks and 
watches measure time by the vibrations of pendulums 
or the oscillations of balance-wheels, the uniformity of 
the action of which depends on the uniformity of their 
size. When the temperature rises, the rod of a pendu- 
lum lengthens, and its vibrations are made more slow- 
ly ; the clock to which it is attached loses time. When 
the temperature declines, the pendulum shortens; it 
beats too quickly, and the clock gains. Similar obser- 
vations may be made in the case of watches. To obvi- 
ate these difficulties many contrivances have been in- 
vented, such as the gridiron pendulum and the compen- 
sation balance-wheel. Advantage has also been taken 
of such substances as expand but little for a given ele- 
vation of temperature, and thus excellent clocks have 
been made, the pendulum-rods of which were formed 
of a slip of marble, or a rod of baked wood varnished. 

Natural as well as artificial measures of time depend 
on heat. Our unit of time, the day, is the period occu- 
pied by one rotation of the earth on her axis. The time 

What effect has heat on the size of bodies ? What is meant by 
the term form of bodies ? How may water be made to exhibit all the 
forms of matter? Describe the manner in which heat affects meas- 
ures of time. 



14 EFFECTS OF TEMPERATURE. 

of rotation is influenced by the temperature of her mass; 
if it should fall she would become less in diameter, and 
would rotate more quickly. Thus, when we tie a 
weight to the end of a string, and, whirling it round in 
the air, permit the thread to twine round one of our fin- 
gers, as it shortens the revolution of the weight be- 
comes quicker. From such reasoning we ascertain that 
the temperature of the globe has not fallen in 2000 
years, because astronomical observations show that the. 
length of the day has not shortened in that time -j-J-^ 
of a second. There was, however, a period when the 
earth was a molten mass. 

The distribution of heat on the earth's surface de- 
termines the distribution of animals and plants. In 
each climate animals whose constitution suits it have 
appeared. The monkey only lives in the torrid zone, 
and dies of consumption in our latitude ; the white bear 
prefers the frigid regions. Man, from the control he 
acquires by diet, houses, clothing, and fire, can live in 
any region, although his physical appearance and men- 
tal powers are affected by a prolonged residence in an 
unpropitious and unusual climate. The types of plants 
vary entirely with change of climate, that is, change 
in temperature, vegetation being most luxuriant in the 
tropics, while on the snow of the polar regions the red 
snow alga only can live. The same changes in plants 
are seen in ascending a high mountain as in making a 
journey toward the pole, the warmth in both cases de- 
clining, and the vegetation becoming less and less vig- 
orous. 

How do we know that the earth's temperature has not fallen in 
2000 years ? Was it ever higher than at present ? What effect has 
heat on the distribution of animals? What effect on plants ? Why 
can man live in any climate ? 



EXPANSION OF GASES. 15 



LECTURE IV. 



Expansion op Gases and Liquids. — Rudberg's Data. 
— Regularity of Gaseous Expansion. — Hot-air Bal- 
loon. — Changes in Temperature change the Volume 
of a given Weight of Air. — Sanctorio's Thermome- 
ter. — Is affected by the Pressure of the Air. — The 
Differential Thermometer. — Differing Expansion of 
Liquids. — Their irregular Expansion. — The Mercu- 
rial Thermometer. — The Fahrenheit, Centigrade, and 
Reaumur Scales. 

If we compare together the three forms of bodies as 
respects their changes of volume under the influence of 
heat, we shall find that, for a given rise of temperature, 
gases expand the most, liquids intermediately, and sol- 
ids least of all. To this rule but few exceptions are 
known ; liquid carbonic acid, however, expands about 
four times as much as any gaseous body. 

When heated from the freezing to the boiling point 
of water, 

1000 cubic inches of iron become .... 1004 
1000 " " water " .... 1045 

1000 " " air " .... 1365 

Experiment has proved that gases differ among them- 
selves in expansibility, though the differences are not to 
any great extent. Those which can be liquefied expand 
the most. For the permanently elastic gases, atmos- 
pheric air may be taken as the type. The experiments 
of Rudberg and later philosophers show that it expands 
^^ of its volume at 32° for every degree of Fahrenheit's 
thermometer. As the same quantity of gas occupies very 
different volumes at different temperatures, it is neces- 
sary, in this and other such cases, to state some special 
temperature at which the estimate of its volume is made. 
The same gaseous mass occupies a much greater space 

What is the relation of expansion of gases, liquids, and solids? 
Give an exception to the rule. Do gases expand alike ? What is 
Rudberg's law? What substance is taken as the type of gases? 
Why is it necessary to state the temperature at which the estimate 
of volume is made? 



11 



EXPANSION OF GASES. 



at 75° than it does at 32°. In the instance before us we 
consider the original volume to be that which the gas 
would have at 32°, and, as has been said, every degree 
above that point will increase the volume by 4-^- of the 
bulk it then possessed. 

Gases expand with uniformity as their temperature 
increases. Ten degrees of heat produce" the same rela- 
tive effect, whether applied at a low or at a high tem- 
perature. This regularity probably arises from the 
want of cohesion which the gaseous particles exhibit. 
As we shall presently see, it is not observed in the case 
of liquids and solids. 

The change in specific gravity of air, when it is 
warmed, is one of the causes of the rise of Montgolfier 
balloons. These, which were invented in France in the 
year 1782, consist of a bag or globe of light materials, 
such as paper or silk, with an aperture at the lower 
part, through which, by the aid of combustible mate- 
rial, as straw or shavings, the air in the interior may be 
Fig. 9. rarefied. On a small scale, they may 

be made of thin tissue paper, pasted 
together so as to form a sphere of 
two or three feet in diameter, Fig. 9, 
an aperture being cut in the lower 
portion six inches or more in width, 
and beneath it a piece of sponge, 
soaked in spirits of wine, suspended. 
This being set on fire, the flame rare- 
fies the air in the interior of the bal- 
loon, which, though it might be at first flaccid, soon 
dilates, and the whole apparatus will now rise in the 
air precisely on the same principle that a cork rises 
from the bottom of a vessel of water. 

In addition to the heated air, the vapor of water that 
is produced from the burning body assists in the as- 
cension, because it is lighter than air. By decline in 
temperature, the heated air collapses to its original size, 
the steam condenses, and the balloon descends to the 
surface of the earth again. 

In the operation of cupping, the cupping-glass re- 

Do gases expand with uniformity ? Describe the construction of 
the Montgolfier balloon. Why does it rise in the air? What is the 
cause of its descent ? Describe the operation of cupping. 




THE AIR-THERMOMETER. 17 

ceives for a moment the flame of a spirit-lamp, and is 
then quickly applied to the surface of the skin. The 
vapor of water condensing, and the heated air contract- 
ing, a very good vacuum can be made. 

As the volume of air changes so readily with the tem- 
perature, becoming less when cooled and greater when 
warmed, the amount of air that a given measure will 
hold is very different at various places on the earth's 
surface. A vessel that will hold an ounce weight at 
the mean temperature of New- York will hold more in 
the cold polar regions, and less at the tropics. In the 
former the air is more dense, because it is in a con- 
tracted condition by reason of the low temperature, and 
therefore a greater weight is included under a given 
volume ; in the latter, the reverse is the case. The in- 
fluence of such changes in the bulk of the air is well 
seen in the Inca Indians, who inhabit the elevated pla- 
teaus near the city of La Paz, in South America. The 
size of their bodies is much greater than that of average 
men ; and, on examination, this is found to be due to 
increase in the size of the chest, caused by the larger 
lungs that they require in order to secure an equal 
amount of oxygen. 

As the expansion of atmospheric air takes place with 
regularity when the temperature rises, it is sometimes 
employed to measure temperature. The Fig.io. 
air-thermometer, called also Sanctorio's 
thermometer, but .which was invented by 
Galileo about 1603, consists of a tube of 
glass, Fig. 10, terminated at its upper end 
by a bulb, a. The other end of the tube, 
being open, dips beneath the surface of 
some colored water in a cup or reservoir, 
<?, which serves also as a foot or support 
to the instrument. The bulb and part of 
the tube are full of air ; the remainder of 
the tube is occupied by the colored water, 
which, by its movements up and down, indicates chan- 
ges of volume in the included air. To the side of the 
tube a scale of divisions, 5, is affixed. The tube is not 

Why does the weight of air in a given measure vary in different 
places ? What is the peculiarity of the Inca Indians ? Describe 
Sanctorio's thermometer. Who was reallv its inventor? 




IS 



AIR-THEEMOMETEHS. 



Fin. 11. 




arranged tightly in the reservoir, but there is a free pas- 
sage for the air in and out of that part of the instru- 
ment. On touching the ball with the fingers, the air 
within it becomes warm, dilates, and depresses the li- 
quid in the tube ; or, on touching with any cold body, 
it contracts, and the liquid rises. 

This form of thermometer is liable to a difficulty 
which renders it impossible to rely 
upon its indications, except under par- 
ticular circumstances. It is affected 
by variations of atmospheric pressure, 
as well as by changes of heat. To 
prove that this is the case, place such 
a thermometer under the receiver of 
an air-pump, as shown in Fig. 11. On 
producing the slightest wpL'isH 
degree of rarefaction, the 
liquid in the tube is in- 
stantly depressed, and on 
restoring the pressure of the air it returns 
to its original position. 

This difficulty is avoided by a change in 
the form of the instrument, by which at- 
mospheric pressure is altogether avoided. 
A tube, bent as in Fig. 12, has a bulb 
blown on each extremity. The bulbs and 
tube are filled with air, except where 
there is a column of colored liquid that 
serves as an index, and whose movements 
are measured by the aid of a scale. This, 
the differential thermometer, is so called 
because it only indicates the difference in 
temperature between the two bulbs, and 
not their actual warmth. When both 
bulbs are heated, the liquid index is equal- 
ly pressed on both sides, and does not 
move, and the same when both are cooled. 
By inserting a tight instead of a loose 
stopper at c, Fig. 10, that instrument also becomes a 
* differential thermometer. 

Describe the action of Sanctorio's thermometer. What is the dif- 
ficulty with this thermometer ? How may the effect of pressure on 
it be shown ? How is this difficulty avoided^ Describe the differen- 
tial thermometer and its mode of action. 



EXPANSION OF LIQUIDS. 



19 



Different liquids expand differently for the same ther- 
mometric disturbance. This is Fig. 13. 

easily shown by an apparatus, 
as in Fig. 13, in which we have 
two tubes, a b, with bulbs on 
their ends, dipping into a large 
vessel. The tubes and bulbs 
should be of the same size, and 
filled with the liquids to be 
tried to the same height. To 
each a scale is annexed. Let 
one, a, be filled with alcohol, 
and the other, 5, with mercury ; on pouring hot water 
into the vessel two phenomena are witnessed : 1st. Both 
liquids expand ; 2d. They expand unequally when com- 
pared together, the mercury expanding least. 

On being heated from the freezing to the boiling 
point of water, liquids expand as follows : 

Expansion of jLiquids. 




At 32°. 


At 212°. 


Expansion. 


1,000,000 parts of Mercury become 
Water" 

a a q^ it 

" " Alcohol 


1,018,153 
1,016,G00 
1,080,000 
1,111,000 


1 in 55 
1 in 21.3 
1 in 12.5 
1 in 9 



The most volatile liquids are the most expansible. 
This is shown by those which have arisen from the con- 
densation of gases, as cyanogen, sulphurous acid, and 
especially carbonic acid. The latter, warmed from 32° 
to 86°, expands four times as much as atmospheric air. 
In liquids of analogous chemical constitution the ex- 
pansion is nearly the same, if the comparison is made, 
not at the same temperature, but at corresponding tem- 
peratures ; that is, at equal distances from the boiling- 
point. If the same precaution is adopted, many dissim- 
ilar liquids present close resemblances. 

Unlike gases, all liquids expand irregularly as their 
temperature rises, a given amount of heat producing a 
much greater effect at a high than at a low tempera- 
How may it be proved that different liquids expand differently? 
What is the rate of expansion of mercury? water? oil? and alco- 
hol ? What kind of liquids are the most expansible ? What is the 
relation of expansion between liquids of analogous composition? 



20 



THE MERCURIAL THERMOMETER. 



tare. Ten degrees of heat applied to a giyen liquid at 
200° will produce a greater expansion than if applied 
at 100°. The reason appears to be that, as a liquid di- 
lates, its cohesive force becomes less, because its parti- 
cles are being removed farther from each other; and as 
the cohesive force weakens, its antagonistic power, heat, 
produces a greater effect. 

Advantage is taken of the properties of liquids in the 
Fig.u. making of thermometers. For these purposes 
alcohol and mercury are the fluids selected. 
The mercurial thermometer, Fig. 14, consists 
of a fine capillary tube of a lenticular section, 
with a bulb blown at one end. The bulb and 
part of the tube are to be filled with quicksil- 
ver, and the air expelled from the rest of the 
tube by warming the bulb until the metal rises 
by expansion to the top of the tube, and at 
that moment hermetically sealing the glass by 
melting the end of F ^ 15. 

it with a blow- 
pipe. As the ther- 
mometer cools, the 
mercury retreats 
from the top of the 
tube, and leaves a 
vacuum above it. 

It remains now 
to annex such a 
scale to the instru- 
ment as may make 
its indications comparable 
with other instruments. To 
effect this, the thermometer 
is plunged into a vessel con- 
taining melting ice or snow, 
and opposite the point at 
which the quicksilver stands 
is marked 32°. It is then 
transferred to another ves- 
sel, Fig. 15, in which water is rapidly boiling, and in 

Do liquids expand with regularity? What liquids are used for 
thermometers ? Describe the mercurial thermometer and the method 
of making it. How is the scale adjusted ? What point is marked 32° ? 





THEKMOMETKIC SCALES. 



21 



which it is surrounded on all sides by steam, and the 
point opposite which the mercury then stands is marked 
212°. The intervening space is divided 
into 180 eqirai parts; these are degrees, 
and similar divisions are made in the scale 
for all points above 212° and below 32°. 
The zero point, or cipher, is therefore 32 
degrees below the freezing point of water. 

It has been observed that, in the course 
of time, the fixed points of some ther- 
mometers change. This is due to the 
pressure of the air acting on the bulb, the 
thin glass of which yields to a certain ex- 
tent, and the liquid consequently rises in 
the tube. The same effect will often take 
place instantaneously by exposing a ther- 
mometer to a high temperature. It is 
therefore necessary to verify, from time 
to time, the graduations of these instru- 
ments. 

The zero point of the thermometer scale 
is not to be regarded as indicating the to- [120 
tal absence of heat. Observations have 
been made in cold climates of degrees 50° 
below zero, and by the aid of liquefied 
protoxide of nitrogen and bisulphide of 
carbon, —220° has been reached. 

The Florentine academicians, who in- 
troduced the liquid thermometer, em- 
ployed an arbitrary scale, merely dividing 
the tube into a number of equal parts. 
Celsius, a Swede, proposed the melting 
point of ice and the boiling point of water 
as standard fixed points, the interval being 
divided into a certain number of parts. 
Unfortunately t^ns interval is by different 
nations differently divided : in America 
and England, Fahrenheit's scale, described 
above, is used; in France, and on the 

What point on the thermometer is marked 212°? How is the 
space between 32° and 212° divided? What change may occur in 
thermometers? What is meant by the zero? What is the lowest 
temperature yet reached ? Who proposed the standard fixed points? 



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22 EXPANSION OF LIQUIDS AND SOLIDS. 

Continent generally, the Centigrade scale is preferred. 
It marks the melting point of ice as 0°, and the boiling 
of water 100°. In Germany and Russia Reaumur's 
scale is employed ; it has the same zero as the Centi- 
grade, but the boiling of water is marked 80°. It is es- 
sential, therefore, in speaking of thermometric degrees, 
to state what scale is meant, and this is accomplished 
by putting the letter F, or C, or R after the specified 
degree. In this book the Fahrenheit division is always 
used, except in a few cases. In Fig. 16 the three scales 
are, for the sake of comparison, represented side by 
side. 



LECTURE V. 

Expansion of Liquids and Solids. — Importance of 
the Thermometer. — Advantages of Quicksilver and 
Alcohol. — Maximum Density of Water and of other 
Liquids. — Connection with the Duration of the Sea- 
sons. — Ground Ice. — Expansion of Solids. — Tlie 
Pyrometer. — Force of Metallic Expansion and Con- 
traction. — Its Use in the Arts. 

As all measures of space and time are affected by va- 
riations of temperature, the thermometer, which determ- 
ines those variations, must necessarily be one of the 
fundamental instruments of physical science. If we 
state that a given object is a foot long, we must specify 
the temperature at wmich the measure was taken, for 
at a lower temperature it will be less, and at a higher 
more than a foot. In constructing bridges, etc., where 
long masses of iron are used, provision must be made 
for expansion by diurnal and seasonal variations of heat. 
Each tube of the Britannia Bridge across the Menai 
Straits is liable in the course of the day to change three 
inches in length. 

Quicksilver is, for several reasons, eminently fitted to 
be a thermometric fluid. 1st. It can be easily obtained 

Describe the Fahrenheit, Centigrade, and Reaumur scales. How 
are they distinguished from one another in writing? What scale 
is used in this book ? What effect does temperature have on meas- 
ures of space and time? Why is quicksilver suitable for making 
thermometers ? 



MAXIMUM DENSITY OF WATER. 23 

of standard purity. 2d. It expands with greater regu- 
larity than most liquids, and, when in a glass bulb, the 
irregular expansion of the glass almost exactly compen- 
sates the irregularity of the mercury, and hence the 
true temperature is accurately indicated. The total 
expansion of mercury, between 32° and 212°, is 1 part 
in 55.08; between 212° and 392°, 1 in 54.61 ; between 
392° and 572°, 1 in 54.01. 3d. The range of tempera- 
ture between boiling and solidification is from 662° 
to — 39°, about seven hundred degrees. 4th. It does 
not soil or wet the tube in which it is contained, for it 
does not adhere to glass, as water or other fluids would 
do. 5th. It is more quickly affected by a given amount 
of heat than water or alcohol, as we shall see when 
speaking of the capacity of bodies for heat. 

When, however, temperatures which approach or are 
below the freezing point of quicksilver require to be 
measured, alcohol is appropriately used, because at the 
lowest temperature yet reached it does not solidify. It 
may be tinged of any color that is desirable to render 
it visible. 

If some water at 100° is taken and placed in a vessel 
in which its changes of volume can be observed, on re- 
ducing its temperature it will be found, under the gen- 
eral law, to cool as it contracts. As it passes through 
the various degrees down to a point between 39° and 
40°, it steadily diminishes, but below that point, though 
the cooling may progress at the same rate as before, it 
begins to expand, and continues to do so until it reaches 
32°, when it freezes. The same fact is demonstrated 
on warming water at 32°: it contracts till 39° is reached, 
and then expands. 

It is obvious, therefore, if we take water at 39°, that 
it makes no difference whether it be warmed or cooled, 
it will expand. The liquid occupies at that temperature 
the smallest bulk, and is at its greatest density, for nei- 
ther by cooling nor warming can we reduce its dimen- 
sions. This pointie designated <c The point of maxi- 
mum density of water" . 

Is its expansion regular ? When must alcohol be used in thermom- 
eters? What peculiarities does water exhibit in cooling to 32°? 
What is observed on warming it from 32° ? What is the point of 
maximum density of water? 



24 POINTS OF MAXIMUM DENSITY. 

Many other liquids have points of maximum density, 
which are reached before solidifying. In the act of 
turning into a solid, water undergoes a very great dila- 
tation, equal to ^-th of its volume, and hence ice will 
float on water. Several melted metals exhibit the same 
phenomenon, and advantage is taken of the fact in the 
arts. The alloy of which types are formed, or stereo- 
type plates cast, in the act of solidifying expands, and 
forces itself into every part of the mould into which it 
may be poured, copying it perfectly ; the same is true 
of cast iron. But it is impossible to make good cast- 
ings with lead, which contracts as it solidifies, and either 
separates from the mould, or leaves vacant spaces in it. 

The fact that water possesses a point of maximum 
density is connected to a great extent with several re- 
markable natural phenomena. The freezing of water 
on the surface is one of these results. If the water con- 
tracted as it cooled, the colder portions would descend, 
and still water would commence to freeze at the bottom 
first, the solidification extending gradually upward. 
Collections of water would, during the course of a win- 
ter, become solid masses of ice, and would greatly re- 
tard the approach of spring, from the length of time 
they would require for thawing through the non-con- 
ducting water above. But, as things are now arranged, 
the coldest water is the lightest ; it floats on the warm 
water below; solidification takes place only on the sur- 
face, and the layer of ice that forms protects the water 
below from farther refrigeration. When the warm 
weather of spring comes on,, the ice on the surface is in 
the most favorable position for melting, and thus the 
point of maximum density of water comes to be con- 
nected with the duration of the seasons. 

Under certain circumstances, ice, which is then called 
ground or anchor ice, does form at the bottom of wa- 
ter instead of on the surface. In clear, rapid, rocky 
streams, the turbulence of the current causes the whole 
mass of water to become so uniformly mixed that there 
is no expanded cold layer floating on the top w T hen the 

Have other liquids points of maximum density ? Give examples. 
What has the maximum density of water to do with the seasons? 
Explain what occurs in the freezing of water. What is ground or 
anchor ice ? 



EXPANSION OF SOLIDS. 



25 



freezing point is attained. As radiation proceeds from 
the plants and rocks at the bottom of the stream, ice 
commences to form on their irregular surfaces in spongy 
masses, occasionally damming up the stream. Not in- 
frequently it floats to the surface, bearing with it masses 
of rock. 

When salt is added to water, the point of maximum 
density descends, until it eventually sinks below the 
freezing point. In the ocean the mass of water is so 
great that, although the maximum density is below 32°, 
the winter does not last sufficiently long to reduce the 
whole to the frozen condition. 

It has already been shown by the instrument repre- 
sented in Fig. 1 that solids dilate on being heated. The 
same results may be rendered apparent by the appara- 
tus Fig. 17, which consists of a board having two up- 

Fig. 17. 




rights, between which a metallic bar, provided with a 
handle, fits so as to permit a rattling noise when it is 
moved in the direction of its length. If the bar be 
heated by pouring hot water upon it, it will dilate to 
such an extent as to be with difficulty forced into place, 
and will no longer rattle. Hearing often aids us to de- 
tect intervals invisible to the eye. 

The pyrometer, of which we have several varieties, 
is represented in Fig. 18. It may serve to illustrate the 
fact that solid substances expand by heat. It consists 
essentially of a metallic bar, a a, resting at one end against 
an immovable prop, e ; the other end bearing upon a 
lever, b. The extremity of this lever presses upon a 
second lever, e, which also serves as an index. Upon 

Explain its formation. What effect has the addition of salt to 
water on the point of maximum density? Explain Fig. 17. What 
fact does it illustrate? What is the use of pyrometers ? Explain 
the construction of Fig. 18. Describe its action. 

B 



26 



EXPANSION OF SOLIDS. 




Fi 9- 18 - the index-lever a. 

spring acts so as 
to oppose the le- 
ver b, and the 
point of the in- 
dex ranges over a 
graduated scale, 
d. 

If lamps be ap- 
plied to the bar 
it expands, and 
the pressure, tak- 
ing effect on the lever, puts it in motion, the index trav- 
ersing over the scale. On removing the lamps the bar 
contracts, and the spring, pressing the lever in the op- 
posite direction as soon as the bar is cold, brings the 
index back to the original point. 

The force with which such expansions take place is 
enormous, being equal in amount to that which would 
be required to elongate or compress the material to the 
same extent by mechanical means. For a variation of 
80° as between the cold of winter and heat of summer, a 
wrought-iron bar 10 inches long will vary in length 
-^_ of an inch, and will exert a strain equal to 50 tons 
on the square inch. This property is useful in the arts, 
where bands of iron are shrunk on wheels, cannon, etc. 
Being made somewhat too small to fit when cold, on 
heating they expand enough to be slipped on, and when 
cooled adhere tightly. For the same reason, boiler riv- 
ets are made red-hot. 



How much force is required to expand a metal bar ? How much 
does a bar 10 inches long expand for a temperature of 80°? Of 
what use is this fact in the arts ? 



CONTEACTION OF SOLIDS. 27 



LECTURE VI. 



Expansion of Solids. — They regain their Size on cool- 
ing. — Tliey expand increasingly. — Different Expan- 
sion of various Solids. — The Gridiron Pendidum. — 
Table of Expansions. — Expansion of crystallized 
Carbonate of Lime. — Solid Thermometers. — Bre- 
guefs Thermometer. — DanieWs Pyrometer. — The 
Thermometer indicates Intensity of Heat. 

It is very commonly supposed that when solid bodies 
have been heated they do not return rigidly to their 
former dimensions on cooling. But a few facts dispose 
of this supposition. A bar of metal exposed to the 
weather is subjected to continual variations of temper- 
ature, warming and expanding when the sun shines* on 
it, cooling and contracting at night. If it did not come 
back t6 its original size exactly, it would be seen to 
grow, and in the course of time it would be much larger. 
The iron railings around public parks and squares never 
increase and become too large for their situations. Sol- 
ids, therefore, on cooling from a warmed state, regain 
the normal size. Lead, however, offers an exception ; 
for, on account of its softness, a leaden pipe used for 
conveying steam will in a short time become perhaps 
several inches longer than at first. Leaden floorings of 
hot-water sinks, also, are thrown into ridges and puck- 
ers. 

By linear dilatation is meant increase in one dimen- 
sion, as in length ; by cubic dilatation, increase in all 
three dimensions, length, breadth, and thickness. Know- 
ing the amount of linear dilatation, the cubic dilatation 
is found nearly enough by multiplying by 3. 

Solids expand increasingly as their temperature rises, 
in that respect resembling liquids, and, for the same 
reason, a diminution of the cohesive force, because of 
the increased separation of the atoms. Compared one 

Do solids regain their size on cooling? What is the reason that 
lead is an exception to the rule ? What is meant by linear dilata- 
tion? What by cubic dilatation? Do solids expand with uniform- 
ity? 



28 



DIFFERENCE OF EXPANSION OF SOLIDS. 



^3 




with another, their rate of expansion is very different, 
a fact shown experimentally by riveting together two 
Fig. 19. bars, one of iron, a a, and one 

of brass, b &, as in Fig. 19. At 
ordinary temperatures the com- 
pound bar is straight, but if 
hot water "be poured on it, it 
curves as at a c, the brass be- 
ing on the outside; while, if cooled below the original 
point, the curvature is in the other direction, as at b c?, 
the brass being on the inside. These changes are due 
to the fact that brass expands and contracts more for a 
given disturbance of temperature than iron. 

By the aid of proper metallic combinations, a bar can 
be constructed that will always remain of the same 
length, regardless of the temperature. The gridiron 
pendulum is made up of two bars of brass and three of 
iron. The expansions being in contrary directions, and 
the lengths being accurately proportioned to the ratio 
of expansion, the ball, or bob, remains at a constant dis- 
tance from the point of support, and the time of vibra- 
tion of the pendulum does noi alter. 

The following table exhibits the expansion in length 
of various substances, when heated from the freezing to 
the boiling point of water : 



English Flint Glass.. 
Glass tube (French)., 

Platinum 

Palladium , 

Untempered Steel 

Antimony , 

Iron 

Bismuth 



1 in 1248 
1 in 1148 
1 in 1131 
1 in 1000 
1 in 926 
1 in 923 
1 in 846 
1 in 718 



Gold 

Copper... 

Brass 

Silver.... 

Tin 

Lead...... 

Zinc 



1 in 682 
1 in 582 
1 in 536 
1 in 524 
1 in 516 
1 in 351 
1 in 340 



Ice is much more expansible than the metals, sur- 
passing even zinc. Glass and platinum may be fused 
together without parting as they cool, for their rates of 
expansion are nearly alike. The process of cutting 
glass with a hot iron depends on unequal expansion. 

Do all solids expand alike ? Describe the compound bar and its 
action. What is the construction of the gridiron pendulum ? De- 
scribe its action. What is the table intended to illustrate ? What 
is the amount of expansion of ice ? Why can glass and platinum 
be fused together without separating on cooling ? 



METALLIC THERMOMETERS. 29 

Rupert's drops are tear-shaped portions of glass, which 
have been formed by dropping that substance while hot 
into water. The exterior being suddenly cooled, while 
the interior is yet fluid, is subjected to a great strain. 
If the tip end of the tail be broken off, the whole drop 
flies into powder. 

Though a solid' is usually regarded as expanding 
equally in all directions, this is not always the case. 
Those crystals which possess the property of double re- 
fraction, and in which all the sides and angles are not 
alike, change their shape when heated. In a crystal of 
calcareous spar the obtuse angles become more acute, 
and the inclination of the faces to each other is made 
8£' less by an elevation from 32° to 212°. The crystal 
elongates most in the direction of the optic axis, and 
contracts in directions at right angles. The general 
bulk, however, increases about 1 part in 510 for the 
above warming. 

Some metallic bodies have points of maximum densi- 
ty in the solid state. Rose's fusible metal, a compound 
of lead, bismuth, and tin, when heated from 32° to 111°, 
expands, but after that contracts, and continues to do 
so till 156°, at which temperature it is less than at 32°. 
After that it again expands, and continues to do so until 
it melts at about 201°. 

Liquid thermometers can not measure the highest 
degrees of temperature, because the vaporization of their 
contents would cause their destruction. For this reason, 
the expansion of one of the more infusible solids, as, for 
example, platinum, must be used, and some contrivance 
similar to Fig. IS employed. The difficulty with such 
apparatus is that the expansion of a short bar of metal 
is so minute that some means of magnifying the effect 
is necessary, and at once irregularity is introduced by 
wheel- work and friction of levers. A compound strip 
of metal is free from these difficulties, and will, if long 
enough, indicate temperatures w r ith great precision. 
Breguet's thermometer consists of a delicate slip of 

What are Rupert's drops? Do solids expand equally in all di- 
rections? Describe the effect of heat on calcareous spar. State 
the peculiarities of fusible metal when heated. For what purposes 
are liquid thermometers inapplicable ? What is the difficulty with 
solid thermometers ? 



30 



METALLIC THEKMOMETERS. 




platinum soldered with gold to one 
of silver, and curved into the form 
of a spiral, a 5, Fig. 20. It is fast- 
ened at its upper end to a metallic 
support, e c, and from its lower end 
an index projects, which plays over 
a graduated circle. As silver ex- 
pands twice as much as platinum, 
when the temperature rises, curva- 
ture, with motion of the index, 
takes place ; when it falls, motion in the opposite direc- 
tion results. The principle is the same as that described 
in the case of the compound bar, Fig. 19. This ther- 
mometer is exceedingly rapid in its indications, because 
the mass of the spiral is so small, as compared with the 
mercury in the bulb of a thermometer. By breathing 
upon it, it will in an instant rise to above 90°. 

For the highest temperatures Darnell's- pyrometer is 
employed. It consists of a bar of platinum inclosed in 
a cylinder of black-lead earthenware. When it is heat- 
ed, as the platinum expands more than the earthenware, 
it presses an index forward, the index remaining pro- 
truded when the pyrometer is taken out of the fire. 
The amount of protrusion is then measured by a scale, 
which converts it into degrees. By its aid it has been 
shown that brass melts at 1869°, silver at 1873°, copper 
at 1996°, gold at 2200°, and cast-iron at 2786°. The 
highest heat of a wind-furnace is 3280°. 

The thermometer does not in reality measure the 
amount of heat in a body. If immersed in a glass and 
a bucketful of the same well-water, it stands at the 
same point, but of course there is much more heat in 
the latter. It measures the intensity, that is, the quan- 
tity contained in a space equal in volume to the mercu- 
ry in the instrument itself. Besides this, though it may 
stand at the same height in the same amount of two 
liquids, it does not follow that they contain the same 
absolute quantity of heat, as we shall see in the next 
lecture. 

Describe Breguet's thermometer, Fig. 20. Give an illustration 
of its sensitiveness. State the reason for it. What is the construc- 
tion of Daniell's pyrometer ? Give the melting points of brass, sil- 
ver, copper, gold, iron. What does the thermometer indicate ? 



SPECIFIC HEAT OF BODIES. 31 



LECTURE VII. 

Specific Heat of Bodies. — Methods of Calorimetry. — 
Warming. — Melting.— Cooling. — Mixture. — Specific 
Heat of various Bodies. — Effect of Physical Condi- 
tion on specific Heat. — Black's Theory of Capacity 
for Heat. — The Dynamical Theory. — Rumford's 
Experiment. 

Many years ago it was discovered by Boyle that if 
two vessels of the same size and form were filled with 
different liquids, and placed before tfae fire so as to re- 
ceive its heat equally, their temperature did not rise 
similarly. If one was filled with water and the other 
with quicksilver, the temperature of the latter would 
rise much more rapidly than that of the former. The 
same quantity of heat will raise the temperature of mer- 
cury twice as high as that of an equal volume of water. 

From a series of similar experiments it has been 
proved that different bodies require different amounts 
of heat to warm them equally. 

Calorimetry. 

There are several different methods by which the 
specific heat of a body may be determined, such as, 1st, 
by warming; 2d, by melting; 3d, by cooling; 4th, by 
mixture. 

The first is that just mentioned as the experiment of 
Boyle, and consists in exposing the same weight of the 
substances to be tried to a uniform source of heat, as, 
for example, a bath of hot water, and observing how 
high the temperature rises in a given time. It will be 
found that it takes thirty times as long to warm water 
as mercury, and hence the specific heat of water is thir- 
ty times greater. 

What was Boyle's discovery ? When two vessels are tilled, one 
with mercury, the other with water, which warms most rapidly? 
What is the comparative effect of the same quantity of heat on wa- 
ter and mercury ? What has been proved to be the law of warming ? 
What methods are there of determining the specific heat of bodies ? 
Describe the method of Boyle. 



32 



CALOEttlETERS. 




The second process is accomplished by the aid of the 
calorimeter, the principle of which 
is illustrated in Fig. 21. A solid 
block of ice, a a, is taken, and in it 
a cavity, 5, is made, the mouth of 
which may # be covered with a slab 
of ice, c c. To determine the rela- 
tive specific heats of water and mer- 
cury, take a flask, <?, and place in it 
an ounce w r eight of water, and, by 
immersing the flask in a bath of hot water, raise its 
temperature to a given point ; for example, 200°. Then 
place it in the cavity, 5, and put on the cover, c c. As 
soon as the temperature of the flask has fallen to 32°, a 
certain portion of the surrounding ice will be found to 
have melted ; this is to be poured out and measured. 

In the same w r ay expose an ounce weight of mercury 
to the same process. The quantity of water melted 
will be only -^ of the amount in the previous case. A 
given weight of water will therefore melt thirty times 
as much ice as the same weight of quicksilver in cool- 
ing through the same number of degrees. 

Lavoisier's calorimeter, Fig. 22, acts on the same 
principle. It consists of a set 
of tin vessels within one an- 
other. In the central one, a 
is the substance to be exam- 
ined. Between this and the 
next is a quantity of broken 
ice, the water from the melt- 
ing of which flows out through 
a stopcock, c, into a graduated 
glass. The vessel b is sur- 
rounded by another, c?, to avoid 
the melting of its ice by the 
warm external air. The water from this is carried off 
by the stopcock, e. Though excellent in principle, the 
difficulties in the practical working of this instrument 
are great. 

The mercurial calorimeter of Favre and Silberman, 

Describe Fig. 21, and the method of using it. What is the rela- 
tive specific heat of water and mercury? Describe Lavoisier's cal- 
orimeter. 




DETERMINATION OF SPECIFIC HEAT. 



33 



Fig. 23, is, -in reality, an enlarged mercurial thermonie- 

Fig. 23. 



a 




ter, the bulb of which may receive the substances to be 
experimented upon. It consists of a glass globe, A, 
with three apertures. Into one of them, 5, is fixed a 
platinum tube, and into this tube a bottle, c, fits, and is 
inclosed by a cork, cL In the tube b is a small quantity 
of mercury, to secure the speedy conduction of heat. 
The aperture e terminates in a stem like a thermometer 
tube, and by the movements of the mercury, /*, along 
the scale, g </, the dilatation of the mercury in A is 
measured. A piston moved by a screw, h, serves to 
bring the mercury, f 9 to the zero of the scale. The 
globe is incased in a box, K, lined with swans' down, 
to avoid disturbance from exterior cooling. The value 
of the degrees is determined experimentally. 

The third process, the method by cooling, consists in 
ascertaining the length of time necessary to cool through 
a definite interval. Water, which has a great specific 
heat, takes a length of time to cool; quicksilver, on the 
contrary, a much less time. The method of cooling re- 
quires several precautions; among others, the substances 
must be placed in vacuo. With liquids it gives very 
good results, but with solids the differing rates of radi- 
ation and conduction render it objectionable. 

The fourth, the method by mixture, is the best. It 
is easily understood. If a pint of water at 40° be mixed 
with a pint of water at 100°, the temperature will be 
the mean, that is, 70°. But if a pint of mercury at 100° 

Describe the calorimeter of Favre and Silberman. What is it in 
reality? In what does the method of cooling consist? What pre- 
cautions does it require ? How is the method by mixture conduct- 
ed? 

B2 



34 



SPECIFIC HEAT OF VARIOUS BODIES. 



be raided with a pint of water at 40°, the temperature 
of the mixture will be 60° ; so that the forty degrees lost 
by the mercury have only raised the water twenty de- 
grees. If equal weights instead of equal volumes of the 
substances are used, the results are more striking, the 
proportion being then as 1 to 30 instead of 1 to 2. 

The method of mixture is equally applicable to solids. 
If a pound of copper at 300° be plunged into a pound 
of water at 50°, the resulting temperature is 72°, from 
which it appears that the specific heat of water is about 
ten times that of copper. 

By resorting to the above methods the specific heat 
of a number of substances has been ascertained, but as 
it is not the absolute quantity of heat that is determined, 
it is necessary to have some standard of comparison. 



Fig. 24. 



For solids and liquids water 
has been chosen, its specific 
heat being the highest, while 
for gaseous bodies air is used. 
The varying specific heat 
of bodies may be illustrated 
by Fig. 24, which consists of a 
cake of wax, C, supported on 
a stand, D, and a number of 
equally warmed balls of vari- 
ous substances. Those which 
have a high specific heat can 
melt their way through the 
wax, and fall to the table, and 
those which have less only 
melt partly through. 

Specific Heats of Equal Weights betioeen 32° and 212°. 




Water 1.00000 

Oil of Turpentine... 0.42593 

Charcoal 0.24150 

Glass 0.19768 

Iron 0.11379 

Zinc 0.09555 

Copper 0.09515 



Brass ;.... 0.09391 

Silver 0.05701 

Tin 0.05623 

Mercury 0.03332 

Platinum 0.03243 

Gold 0.03244 

Lead 0.Q3140 



How do we know that the specific heat of water is ten times that 
of copper ? Why is a standard of comparison for specific heat neces- 
sary ? What are the substances used as standards ? Describe Fig, 
24. What does it illustrate ? 



black's theory of capacities. 35 

The specific heat of a substance varies with its phys- 
ical condition. Water, when solidified into ice, has 
only one half the specific heat, as 505 to 1000. In the 
form of steam there is also a diminution, the ratio being 
as 480 to 1000 for equal weights. Mechanical compres- 
sion also alters the specific heat, copper, which had stood 
at 0*950, by hammering being reduced to 0*936. On an- 
nealing, it, however, regained its primitive condition. 
In dimorphous bodies, the densest form has the low- 
est specific heat, diamond, for instance, being 0*1468; 
graphite is 0*2018, and charcoal 0*2415. 

Dr. Black, who was one of the early investigators of 
heat phenomena, introduced a term, " Capacity of bod- 
ies for heat," implying the idea that this principle, en- 
tering their pores, was taken up by different bodies to 
different amounts, in the same way that two sponges 
of different densities will hold different quantities of 
water. On this supposition, the lighter a body is, the 
greater should be its capacity for heat, because its at- 
oms are more widely separated. But in practice this is 
found not to be the case, oil, that floats on water, not 
having half the capacity for heat that the water has. 

The specific heat of bodies increases with their tem- 
perature. On Black's doctrine, this is accounted for by 
saying that the atomic interstices become larger, and 
there is more room for the heat. In the process of 
compression by hammering, heat is evolved, and, accord- 
ing to Black, this is due to the forcing of the atoms to- 
gether, which causes the exudation of some of the heat. 
But it can not be supposed that the great heat which is 
produced can all arise from such a source. According 
to the dynamical theory of heat, it results from a con- 
version of mechanical motion into molecular motion, 
heat being regarded not as a substance, but as a motion 
of the atoms of bodies. 

An experiment by Rumford illustrates this point. 
He took a hollow cylinder of iron, into which a plunger 
was fitted, an<l caused to press against the bottom. A 

How may the specific heat of a substance be varied ? What is 
meant by capacity for heat? Give an illustration. Why is the 
specific heat of bodies decreased by hammering, on Black's theory? 
How is it accounted for on the dynamical theory ? Describe Rum- 
ford's experiment. 



36 THE DYNAMICAL THE0KY. 

box containing 18| pounds of water surrounded the 
cylinder ; its temperature, which was, at the beginning 
of the experiment, 60°, was marked by a thermometer. 
The cylinder was turned by a horse, and in an hour 
after the friction had commenced the temperature was 
107°. At the end of two hours and a half the water 
actually boiled. The quantity of metal abraded, and 
from which, according to the material theory, this great 
amount of heat must have been produced, was only a 
few hundred grains. In addition to this, he found that 
the chips had the same capacity for heat as before, and 
hence concluded that the mechanical motion had been 
converted into heat. 

There is also a very significant experiment of Davy 
which indicates the same fact. Ice has only one half 
the capacity for heat that water possesses ; and, in ad- 
dition, an immense amount of heat- must be consumed 
in changing it to the liquid condition. But Davy, by 
friction of two pieces of ice together, produced water, 
and yet the original quantity of heat in the ice was but 
a small fraction of that in the water. The extra amount 
must have been furnished by the mechanical motion 
used. 



LECTURE VIII. 

Specific Heat and Latent Heat. — Variability of S}oe- 
cific Heat wider Compression and Dilatation. — The- 
ory of the Formation of Clouds. — TJie Fire Syringe. 
— Cold of the Upper Regions of the Air. — Connec- 
tion between Specific Heats and Atomic Weights.— 
Latent Heat. — Melting Points of various Bodies. — 
Latent Heat of Water and other Bodies. 

The capacity of gases for heat is determined by 
warming a known weight by means of a spiral tube im- 
mersed in hot oil, and then conducting the gas through 
a vessel surrounded by a known weight of water. The 
inquiry is attended by very great difficulties. 

When the volume of a gas increases its capacity for 

What did Rumford conclude? What was Davy's experiment? 
What conclusion did he come to ? How is the capacity of gases for 
heat determined ? 



VARIATIONS OF SPECIFIC HEAT. 



37 




heat increases, and a diminution of volume is attended 
with a diminution of capacity. If a Bre- p^.25. 
guet's thermometer be placed under the re- 
ceiver of an air-pump, which is rapidly ex- 
hausted, Fig. 25, a sudden reduction of tem- 
perature is indicated. As the rarefaction 
proceeds the capacity for heat increases, an 
increase which is satisfied at the expense of a 
portion of the sensible heat. 

On the same principle, the appearance of the fog or 
cloud, which comes when moist air is rarefied, is ex- 
plained. The quantity of vapor that can exist in a giv- 
en space depends on the temperature. If the space is 
cooled, a portion of the vapor will condense. When, 
by suddenly rarefying air, we increase its capacity for 
heat, the temperature falls, and part of its moist- 2^.20. 
ure assumes the form of drops. If a bell-jar is 
taken, the inside having been rinsed out with 
water and placed on the air-pump stand, on ex- 
hausting, a mist makes its appearance, which 
immediately clears up on readmitting the air, 
A candle placed behind the jar will show the 
effect to a large audience. 

When air is suddenly compressed, its capaci- 
ty for heat diminishes. This is experimentally 
shown by the fire-syringe, Fig. 26, which con- 
sists of a strong glass tube, containing a tightly- 
fitting piston. By forcing the piston down- 
ward, the air in the cylinder can be compressed. 
If a piece of cotton, moistened with bisulphide 
of carbon, be put into the syringe previously, a 
brilliant flash of light will follow the compres- 
sion. Even tinder may be set on fire in the 
same way. 

The variation in capacity of substances with 
variation of volume was explained on Black's 
doctrine, as follows : If a sponge soaked in wa- 
ter be compressed, a portion of the water ex- 

What effect does change in volume of a gas have on its capacity for 
heat? Describe the experiment Fig. 25. Explain the appearance 
of fog in rarefying air. How may this be illustrated experimental- 
ly? Describe the fire-syringe and its method of action. How is 
the variation in capacity for heat explained on Black's theory ? 



38 



VARIATIONS OF SPECIFIC HEAT. 



udes, just as in the syringe the air allows heat to escape. 
On relaxing the sponge, it will take up more water, just 
as aii # , when dilated, has its capacity for heat increased. 
According to the dynamical theory of heat, the heat 
developed during compression would be regarded as a 
conversion of the muscular movement of the arm into 
molecular motion of the atoms of air. 

The great degree of cold which prevails in the upper 
regions of the atmosphere, as is shown by the following 
table, is due, to a considerable extent, to the capacity 
of that dilated air for heat. 



Altitude 
in feet. 


Temperature. 


Altitude 
in feet* 


Temperature. 


Altitude 
in feet. 


Temperature. 




5.000 

10,000 


80° 
64°.4 

48°.4 


15,000 
20,000 


31°.4 
12°.8 


25,000 
30,000 


- 7°.6 

-30°.7 



The formation of clouds is also explained on the same 
principle. A stratum of air resting on the. sea or moist 
earth becomes saturated with moisture, and by the 
warmth of the sun begins to rise through the atmos- 
phere. As it rises it expands, on account of the de- 
creasing pressure, and its capacity for heat increases. 
A portion of the moisture is therefore deposited in the 
form of drops, and constitutes a cloud. 

The small capacity of quicksilver for heat renders it 
a suitable liquid for thermometers, because it cools or 
warms rapidly, and follows variations of temperature 
more quickly than water and most other fluids. 

There is a connection between the specific heat of 
bodies and their atomic weights. In most cases, if sub- 
stances are compared together in the ratio of their com- 
bining proportions, it will be found that the same amount 
of heat will raise them an equal number of degrees ; 
that is, the specific heat of an elementary body is in- 
versely as its combining proportion. In the exceptional 
cases there is generally some simple multiple relation, 
as is shown in the following table : 

How is the variation in the capacity for heat explained on the dy- 
namical theory ? What is the cause of the cold in the upper regions 
of the air? What is the temperature at 30,000 feet? Explain the 
formation of clouds. Why is quicksilver specially suitable for ther- 
mometers ? What is the relation between specific heat and atomic 
weight ? 



LATENT HEAT. 



39 



Table of the Specific Heats of the Elementary Atoms. 



Iron 3.18G1 

Zinc 3.1054 

Copper... 3.0162 

Lead 3.2530 

Tin 3.3063 

Nickel 3.2045 

Cobalt 3.1553 

Platinum 3.1976 



Sulphur 2.8416 

Mercury 3.3320 

Silver 6.1570 

Arsenic 6.1050 

Antimony 6.1939 

Gold 6.3777 

Iodine.... 6.8732 

Bismuth 6.4764 



From this table it appears that theiirst ten substances 
show a close approximation in their capacities for heat, 
if the quantities used be in proportion to the atomic 
weights instead of equal weights. The remainder have 
a double capacity. In compounds the specific heat may 
be calculated from the sum of the atomic heats of their 
components. 

Latent Heat. 
First Change of Form. — Heat of Fluidity. 
When solid substances, which can resist a high tem- 
perature without decomposition, are exposed to an in- 
creasing heat, a point is eventually reached at which 
they assume the liquid state. This point, known as the 
point of fusion, or melting point, is fixed for each sub- 
stance. 

Table of the Melting Points of Bodies. 



Mercury —39 

Oil of Vitriol -30 

Bromine 9.5 

Ice 32 

Phosphorus 111.5 

Potassium 136 

Yellow Wax 143.6 

Sodium 207.7 

Iodine 224.6 

Sulphur , 239 

Tin 451 



Bismuth 512 

Nitrate of Soda 591 

Lead 620 

Nitrate of Potassa..,. 642 

Zinc 773 

Silver 1773 

Copper 1996 

Gold 2016 

Cast Iron 2786 

Wrought Iron { a J™ 



Some substances, perhaps all, to a greater or less ex- 
tent, pass through a condition intervening between the 
solid and liquid state, assuming a pasty consistency. 

What quantities of substances must be used instead of equal 
weights ? What change inform occurs on heating solid substances ? 
State the melting points of various bodies — mercury, oil of vitriol, 
etc. What intermediate condition may substances pass through? 



40 LATENT HEAT. 

The manufacture of glass depends on such a property. 
It is also shown strikingly by various oils and wax. 
Indeed, different liquids may be said to present different 
degrees of liquidity. This is well seen when sulphuric 
acid, a dense, sluggishly-moving body, is compared with 
sulphuric ether, a substance of remarkable mobility. 
The liquidity of the liquid state seems generally to be 
increased by elevation of temperature. 

If we take a mass of ice, the temperature of which is 
at the zero point, arfd bring it into a warm room, examin- 
ing the circumstances under which its temperature rises, 
they will be found as follows : the mass of ice, like any 
other solid body, warms with regularity until it reaches 
32° ; then, for a considerable period of time, no farther 
elevation is perceptible, but it undergoes a molecular 
change, assuming the liquid condition; when this is 
complete, the temperature again commences to rise. 

That we may have precise views of these facts, let us 
suppose that the mass of ice and the warm room into 
which it is carried have such relations to each other 
that the temperature of the former can rise from the 
zero point one degree per minute; for thirty-two min- 
utes the temperature of the ice will be found to increase, 
and at the end of that time, a thermometer, if applied, 
would stand at 32°. But now, although the heat is 
still entering the ice at the rate of a degree per minute, 
the process of warming ceases, and for 142 minutes no 
farther rise takes place, but the ice melts, and is com- 
pletely liquefied at the end 'of that time. The temper- 
ature then again steadily rises, and continues to do so 
with regularity. 

We know, from experiments like the foregoing, that 
about 142 degrees of heat are absorbed by ice in pass- 
ing into the condition of water ; and, as this heat is not 
discoverable by the thermometer, it is designated as 
latent heat. 

A similar fact appears when any liquid, such as wa- 

Give an example of the intermediate condition substances may 
pass through. Give an example of different degrees of liquidity. 
Describe what occurs on warming ice. At what degree does its 
temperature remain stationary for a time ? How long is the pause ? 
What change in form occurs at the same time ? What is meant by 
latent heat? 



i 



LATENT HEAT OF BODIES. 41 

ter, passes into the vaporous condition. If some water 
be exposed to a fire which can raise its temperature at 
the rate of one degree per minute, that effect will con- 
tinue till 212° are reached ; at that point, no matter how 
much the heat be increased, the temperature remains 
stationary. The water undergoes a change of form, 
assuming the condition of a vapor, and the change is 
completed in about 967 minutes. In this, as in the for- 
mer instance, we infer that a large amount of heat has 
become latent, or undiscoverable by the thermometer, 
and that it is occupied in establishing the elastic form 
which the water has assumed. 

Table of Latent Heat of Bodies. 



F.° 



Water 142.65 

Nitrate of Soda 113.34 

Nitrate of Potash 85.26 

Zinc 50.63 

Silver 37.92 

Tin. 25.65 

Cadmium 24.44 

Bismuth 22.75 

Sulphur 16.85 

Lead 9.65 

Phosphorus 9.05 

Mercury 5.11 



Water =1. 



1.000 
.794 
.598 
.355 
.265 
.179 
.171 
,159 
.118 
.067 
.063 
.035 



By the method of mixtures the same results may be 
established. Thus, if a pound of water at 32° be mixed 
with a pound at 174°, the mixture will have the mean 
temperature, that is, 103° ; but if a pound of ice at 32° 
be mixed with a pound of water at 174°, the mixture 
still remains at 32° ; and the reason is clear, from the 
foregoing considerations, that ice, in passing into the 
liquid state, requires 142° of latent heat. 

At what point does water pause when warmed ? How many de- 
grees of heat are required to vaporize water ? What has become of 
the heat? Do all substances have the same amount of latent heat? 
How can the doctrine of latent heat be proved by the method of 
mixture ? 



42 HEAT OF SOLIDIFICATION. 



LECTURE IX. 

Latent Heat. — Heat evolved in Solidification— Theo- 
ry of Freezing Mixtures. — Expansion during Solidi- 
fication. — Freezing and Melting Point of Water. — 
Its Latent Heat affects the Duration of Autumn and 
Spring. — Begelation. — Heat of Elasticity. — Boiling 
Points of various Liquids. — Nature of Vapor. 

When a liquid assumes the solid form a considerable 
amount of beat is evolved. The cause is readily under- 
stood from what we have seen taking place during the 
reverse process, which has led us to the fact that the 
difference between any given solid and the liquid which 
arises from it by melting is in the large amount of la- 
tent heat which is found in the latter, and w T hich is oc- 
cupied in giving it its form. 

A saturated solution of sulphate of soda may be cooled 
from its boiling point to common temperatures in a ves- 
sel tightly corked without solidification taking place, 
but when the cork is withdrawn, crystallization ensues, 
and heat is evolved. This may be proved by taking a 
bottle filled with such a solution, and, having introduced 
the bulb of an air-thermometer through the neck by 
means of an air-tight cork, the mouth of the bottle is to 
be carefully stopped. When the w T hole apparatus has 
reached the ordinary temperature of the air the stopper 
is withdrawn, and solidification at once takes place ; or, 
if it should at first fail, the introduction of a crystal of 
sulphate of soda will bring it on. At that moment it 
will be perceived that not only does the thermometer 
indicate a rise of temperature, but, if the bottle be 
grasped, it will be found to be sensibly warm. 

On these principles depends the action of freezing 
mixtures, of which the following is an example. If we 
fcake 8 parts of crystallized sulphate of soda and mix it 

What becomes of the latent heat of a fluid when it solidifies? 
What is the difference between the solid and liquid forms of a sub- 
stance? Describe the experiment with sulphate of soda. What 
change of temperature is seen? Describe the action of a freezing 
mixture. 



FKEEZING MIXTURES. 43 

in a thin tumbler with 5 parts of hydrochloric acid, the 
sulphate of soda, from being a solid, assumes the liquid 
form ; and taking, in order to effect that change of form, 
heat from surrounding bodies, it reduces their temper- 
ature. This may be shown by placing 4 parts of water 
in a thin glass test-tube and stirring it about in the 
mixture ; the water speedily freezes, even on a summer 
day. 

Table of Freezing Mixtures, 



Mixtures. # 


Reduction of Tem- 
perature. 


Nitrate of Ammonia 1, "Water 1 


From 50° to 4° 
" 50° to 
" 50° to - 4° 
" to -46° 


Sulphate of Soda 8, Hydrochloric Acid 5.. 

Snow or Ice 2, Common Salt 1 

Snow 3 Dilute Nitric Acid 2 





All these mixtures depend essentially on the princi- 
ple under consideration, that latent heat must be fur- 
nished to a substance passing from the solid to the 
liquid state; a cubic yard of ice would require a bushel 
of coal to melt it. They consist of various solid sub- 
stances, the liquefaction of which is brought about by 
the action of other bodies. Even during the liquefac- 
tion of an alloy by quicksilver the same thing is ob- 
served. An alloy of lead, tin, and bismuth, dissolved 
in mercury, will cause a thermometer to sink from 63° 
to 14°. 

Many substances, when solidifying, expand. This is 
the case with water, in which the amount of expansion 
is about -^-th of the bulk. The force which is exerted 
under these circumstances is very great, and capable of 
tearing open the strongest vessels. This may be shown 
by filling a bottle with water, and fastening the cork 
down tightly with wire. On putting it into a freezing 
mixture, congelation promptly takes place, and the bot- 
tle is burst. An iron bottle filled with melted bismuth, 
and allowed to cool, is broken in the same manner. 

The freezing point of w r ater is usually spoken of as a 
fixed point, and is marked as such upon the scales of 
our thermometers, but if water be cooled without agi- 

Why is cold produced? Give examples of other freezing mix- 
tures. What is the essential principle of freezing mixtures? What 
is the amount of expansion of water in freezing? How may the 
force exerted be shown? Is the freezing of water a fixed point? 



44 FREEZING POINT OF WATER. 

tation it may be brought as low as 15°. By causing 
the freezing to take place in very strong vessels of steel. 
Mousson found that under a pressure of 13,000 atmos- 
pheres water remained liquid at 0°, and that if ice were 
introduced- into the apparatus, on applying pressure, it 
was unable to preserve the solid state ; its bulk was re- 
duced at 13,000 atmospheres by y 1 ^ of the volume at 
32°. 

But though water will retain its liquid form far below 
its freezing point, ice can not be brought above 32° 
without melting. The melting of ice is, therefore, the 
fixed thermometric point. 

We have seen that the possession of a point of maxi- 
mum density by water exerts a great effect upon the 
duration of the seasons; a similar observation might be 
made as respects its latent heat. If ice, by the absorp- 
tion of a single degree of heat when it passes from 32°, 
could turn into water, the great deposits of winter 
would suddenly melt, and inundations be frequent, just 
as when Etna pours a torrent of lava down its snow- 
clad sides, the flood is more destructive than the molten 
mass ; or if water, by losing a single degree of heat, 
turned into ice, freezing would go on with great rapid- 
ity. To the melting of snow or the freezing of water 
time is necessary; the 142° degrees of latent heat have 
to be disposed of; this, therefore, serves to procrasti- 
nate the approach of winter, and causes the spring to 
come on more slowly. 

If two pieces of ice at 32°, with moistened surfaces, 
are placed in contact, they freeze to one another. This 
phenomenon is called regelation, and will occur, though 
the air may be at 90°, or the ice be in water of that 
temperature. In the same way, flannel, hair, or cotton 
will freeze to ice, though the metals will not. By plac- 
ing fragments of ice in wpoden moulds, as in Fig. 27, 
C D,' H P, and applying a severe pressure, spheres, as 
B, cups, lenses, etc., may be formed. The cause of the 
refreezing has not been ascertained up to the present. 
Regelation explains the original formation of glaciers 
from damp snow, and accounts for their motions and 

Describe Mousson's experiment. Is the melting of ice a fixed 
point ? What effect has the latent heat of water on the seasons ? 
What is meant by regelation ? 



REGELATION. 

Fig. 27. 



45 




changes of form in descending to the valleys below. It 
avoids the necessity of supposing that the ice is a vis- 
cous body. 

Second Change of Form. — Heat of Elasticity. 

Exposed to a rise of temperature, liquid substances 
boil at a particular point, which varies with their nature. 

Table of Boiling Points. 



Sulphuro us Acid . . 17° 

Ether 95° 

Bisulphide of Carbon... 118° 

Bromine 145° 

Alcohol 173° 

Water 212° 



Acetic Acid ( . 243° 

Nitric- Acid 248° 

Oil of Turpentine 314° 

Phosphorus 554° 

Sulphuric Acid. 640° 

Mercury 662° 



A technical distinction is made between a gas and a 
vapor. By the latter we understand a gas which will 



Fig. 28. 



readily take on the liquid form. 

Some of the leading peculiarities in 
the constitution of vapors may be ex- 
hibited by the following experiment: 
take a glass tube, a a, Fig* 28, with a 
bulb, 6, blown on its upper extremity ; 
pour water into the bulb, filling the tube 
to within an inch or two of the end ; this 

What does Fig. 27 illustrate? Do all fluids boil at the same 
point ? Give the boiling points of sulphurous acid, ether, etc. What 
is the distinction between a gas and a vapor? What fact is Fig. 28 
intended to illustrate? Describe the instrument and its action. 




46 



LATENT HEAT OF VAPORS. 



Fig. 29. 



vacant space fill with sulphuric ether ; and now, closing 
the end of the tube with the finger, invert it in a glass 
of water, as is represented in the figure. The ether, be- 
ing much lighter than water, at once rises to the upper 
part of the bulb, as is shown by the light space, the 
bulb being, of course, full of ether and water conjointly. 
On the application of a spirit-lamp the ether vapor- 
izes, and presses the water out of the bulb into the glass 
cup. Three important facts may now be established.. 

1st. Vapors occupy more space than the liquids from 
which they arise. 

2d. They have not a misty or fog-like appearance, but 
are perfectly transparent. 

3d. When their temperature is reduced, they collapse 
to the liquid state. 

It has already been shown that a large amount of 
heat becomes latent, constituting the heat of elasticity 
of vapors. The temperature of steam is 212°, as is that 
of the water from which it rises, but it contains 966° 

of latent heat, which 
give it its new form. 
Different vapors con- 
tain different quanti- 
ties of latent heat: 
ether, 163°; alcohol, 
375°; bromine, 82°; 
iodine, 43°. It is the 
large amount of latent 
heat which makes 
steam so efficient in 
warming. The steam 
arising from one gal- 
lon of water will raise 
the temperature of 
five gallons from the 
freezing to the boil- 
ing point ; its heat of 
elasticity is nearly suf- 
ficient, were the steam 
a solid body, to make 

What facts are established by it ? What is the difference be- 
tween steam and water at 212° ? Do all vapors have the same 
amount of latent heat ? 




VAPORIZATION. 47 

it visibly red-hot in the daylight. In the warming of 
buildings by steam-pipes, each square foot of their sur- 
face will heat 200 cubic feet of the surrounding air to 
75°, and will require about 170 cubic inches of boiler 
capacity for its supply. 

The latent heat of vapors is determined by an appa- 
ratus arranged as in Fig. 29. A is a flask to contain 
the liquid ; _Z?, a receiver with a spiral tube, terminating 
at d. C contains a weighed quantity of water. The 
liquid is distilled into J5, and the rise of temperature 
measured by the thermometer t ; s is a tube for agita- 
tion. H is a tin-plate screen to shut off the influence of 
the lamp. The whole is inclosed in an outer tin vessel, D. 



LECTURE X. 

Vaporization. — ■ Vapors form at all Temperatures. — 
Form instantly in a Vacuum. — Diminution of 
Pressure favors Evaporation. — Elastic Force of Va- 
pors. — Cumulative Pressure of heated Vapor. — Re- 
striction on Marriotts Eaw. — Elasticity increases 
with Temperature. — Maximum density of Vapors. — 
Liquefaction of Gases. 

Vaporization goes on at all temperatures. It is not 
necessary that the boiling point should be reached ; 
even ice will evaporate away, and, if put in the vacuum 
of a barometer, will depress the mercurial column. The 
thin films of this substance often seen incrusting win- 
dows may disappear without melting, %nd a mass of 
ice freely exposed to the air on a dry frosty day loses 
weight. So camphor is constantly giving off a vapor, 
which crystallizes on the cold side of the bottle contain- 
ing it. Steam, therefore, rises from water at all tem- 
peratures, but with more rapidity and a higher elastic 
force as the temperature is higher. 

In a vacuum vapors form instantaneously. If a num- 
ber of barometer tubes, Fig. 30, be taken and filled with 
mercury in the usual manner, the difference of volatility 

Describe Fig. 29. What is its object? Is vaporization limited to 
any particular temperature? How can it be proved that ice may 
evaporate? What is the effect of a vacuum on vaporization ? 



48 



EVAPORATION. 



of various substances may- 
be shown. Let 1 be kept 
as a standard of reference. 
Pass a few drops of wa- 
ter into 2, of alcohol into 
3, of bisulphide of carbon 
into 4, and of ether into 
5. The mercury will be 
progressively more and 
more depressed in each 
case. 

Diminution of pressure 
favors evaporation, and 
many liquids Avould be 
permanently gaseous if 
the pressure of the air 
were removed. Fig.%\. 
Take a glass 
tube, A, Fig. 
31, closed at one 
end, and, hav- 
ing filled it with 
water, invert it 
into a cup, B, 
and introduce into it a 
little sulphuric ether, which will rise to a. On covering 
the whole with an air-pump jar, and exhausting, the 
ether boils, and gives off a transparent vapor. On re- 
admitting the air, the ether goes back to the liquid con- 
dition. By increase of pressure, as well as by diminu- 
tion of temperature, vapors may be condensed. 

In the process of evaporation, vapor ft supplied only 
from the surface, and consequently is more rapid as the 
surface is larger. In the salt-works of Salzburg the 
brine is made to trickle through brushwood, and the 
water evaporates with great quickness. By covering 
an evaporating surface of water with oil, evaporation is 
entirely suspended. 

Though vapors occupy more space than the liquids 
from which they come, the increase of volume is by no 

Describe the instrument Fig. 30. What effect has diminution of 
pressure on vaporization? Describe Fig. 31. What effect has sur- 
face on evaporation ? 





ELASTIC FORCE OP VAPORS. 



49 



Fig. 32. 



no means the same in all cases. At the ordinary pres- 
sure, a cubic inch of water produces 1696 cubic inches, 
nearly a cubic foot, of steam ; alcohol, 528 ; ether, 298 • 
oil of turpentine, 193. Hence, though the three last- 
named liquids take up less latent heat than water in va- 
porizing, they could not be economically used in a 
steam-engine, because the expansive force is propor- 
tionately less, a smaller bulk of vapor being given off. 
_ The elastic force exerted by vapors within certain 
limits can be measured by the apparatus Fig. 30. The 
theory of the process is very simple. The height at 
which the barometer stands is determined by the press- 
ure of the air. As long as there is nothing 
to counterbalance that pressure, the mercury 
is forced up by it in the tube to a height of 
30 inches ; but on introducing some ether, 
as at a a, Fig. 32, the vapor which forms, 
exerting an elastic force in the opposite di- 
rection, tends to push the mercury out of 
the tube. On the one hand, we have the 
pressure of the air; on the other, the elastic 
force of the ethereal vapor ; they press in 
opposite directions, and the resulting alti- 
tude at which the mercury stands expresses, 
and indeed measures the elastic force of the 
vapor. Thus, at a temperature of 80°, wa- 
ter will depress the mercurial column about 1 inch al- 
cohol about 2 inches, and sulphuric ether about '20 
lnese numbers, therefore, represent the 
elastic force of the vapors evolved. 

In close vessels, from which there is 
no escape, or from which the escape is 
greatly retarded, a constantly accumu- 
lated force is generated when the tem- 
perature is raised. Thus, if we place 
some water in a flask, a, Fig. 33, into 
which a tube, b 6, is inserted air-tight 
by means of a cork, and bent in the 
form exhibited in the figure, and dip- 
Do all liquids expand equally in assuming the vaporous state ? 
liow may the elastic force of vapors be measured by the barome- 
ter t What is the principle involved ? What results from heating 
a liquid in a close vessel ? Describe Fig. 33 

c 




Fig. 33. 





50 marriotte's law. 

ping nearly to the bottom of the flask, on the appli- 
cation of a spirit-lamp, the vapor generated, having 
no passage of escape, accumulates in the upper part 
of the flask, and, exerting its elastic force, presses 
the liquid through the tube in a continuous stream. 
The mechanical force which thus arises when every av- 
enue of escape is stopped, is strikingly exhibited by the 
little glass bulbs called candle-bombs. These are small 
globules of glass about as large as a pea, with a neck 
an inch long ; into the interior a drop of water is intro- 
duced, and the termination of the neck hermetically 
sealed by melting the glass. When 
one of these is stuck in the wick of 
a candle or lamp, as in Fig. 34, the 
heat vaporizes a portion 'of the wa- 
ter, and, there being no passage 
through which the steam can escape, 
the bulb is burst to' pieces with a 
loud explosion, a mechanical force* 
which is wonderful, when we consid- 
er the amount of water employed. It is a miniature 
representation of what takes place on the large scale in 
the bursting of high-pressure steam-boilers. 

Marriotte's law, which assigns the volume of a gas 
under variations of pressure, applies, under certain re- 
strictions, to the case of vapors. A permanently elastic 
gas, when the pressure is doubled, contracts to one half 
of its former volume ; if the pressure be tripled, to one 
third, and so on; but not so with vapors. If upon 
steam, as it rises from water at 212°, any increase of 
pressure be exerted, this vapor at once loses its elastic 
form, and instantly condenses into water. But vapors, 
like atmospheric air, if the pressure upon them be di- 
minished, follow Marriotte's law. Thus, if the pressure 
be reduced to one half, steam at once doubles its vol- 
ume. For vapors, Marriotte's law, therefore, holds for 
diminutions of pressure ; but when the pressure is in- 
creased it apparently fails, the vapors relapsing into the 
liquid form. 

That the elasticity of a vapor increases with its tem- 

What is the construction of a candle-bomb? What is Marriotte's 
law? Does it apply to vapors? What is the effect produced by in- 
creasing the pressure on a vapor ? 



ELASTICITY OF VAPORS. 



51 



perature may be readily proved by 
taking a tube one third of an inch in 
diameter, and 30 inches long, closed 
at one end, «, Fig. 35, with ajar, 5, 
an inch or more in diameter, and 30 
inches deep. Let the tube be rilled 
with quicksilver, so as to leave . a 
space of half an inch, into which 
ether may be poured; invert the 
tube in the deep jar, also containing 
quicksilver; the ether, of course, 
rises to the other closed extremity. 
If the tube be lifted in the jar as 
high as possible without admitting 
external air, a certain portion of the 
ether will vaporize, and, depressing 
the quicksilver, its elastic force may 
be measured by the length of the 
resulting column. If now the closed 
end of the tube be grasped in the 
hand, or if it be slightly warmed by 
the application of a lamp, the mer- 
curial column is at once depressed, 
proving that the elastic force of the 
vapor is increasing. As soon as the 
tube is warmed to the boiling point 
of the ether, the column of mercury 
is depressed exactly to the level on 
the outside of the tube. At this 
point, therefore, it balances, or is equal to the pressure 
of the air. 

Now let the tube be depressed in the jar, it will be 
seen with what facility the vapor reassumes the liquid 
condition. As the tube descends the vapor condenses, 
and the mercury keeps constantly at the same level. 
On raising the tube fresh portions of the ether vapor- 
ize, the mercury still retaining its height above the gen- 
eral level. There is, therefore, a point of maximum 
density for each temperature when the vapor is in con- 
How may the relation between the elasticity of a vapor and the 
temperature be shown? What effect is seen on warming the tube, 
Fig. 35 ? When the tube is warmed to the boiling point of the ether 
what is seen ? 




52 



LIQUEFACTION OF GASES. 



tact with the liquid. It can not be surpassed by in- 
creasing the pressure, because a part of the evaporated 
liquid immediately condenses, while a decrease of press- 
ure causes volatilization of a fresh portion. The point 
of maximum density rises with the temperature of the 
vapor. The density of air at 212° being taken as 1000, 
that of the vapor of water at its maximum density will 
be as follows : 

Table of the Maximum Density of Water Vapor. 



Temperature. 


Density. 


Weight of 100 cubic inches. 


32° 


5.690 


.136 grains 


50° 


10.293 


.247 "• 


60° 


14.108 


.338 " 


100° 


46.500 


1.113 " 


150° 


170.293 


4.076 " 


212° 


625.000 


14.962 " 



The tension or elasticity of all vapors is nearly the 
same, if compared at temperatures which represent dif- 
ferences of an equal number of degrees above or below 
the boiling points of the respective liquids. 

By exerting severe pressure on various gases,.as sul- 
phurous acid, cyanogen, chlorine, carbonic acid, and pro- 
toxide of nitrogen, they have been made to assume the 
liquid condition ; but other gases, as hydrogen, oxygen, 
and nitrogen, may be exposed to a pressure of 58 atmos- 
pheres, and cooled to —140° without liquefying. Air has 
been reduced by pressure to -^-^ of its volume, and sub- 
jected to a bath of ether and solid carbonic acid (—1.66°) 
without changing its form. 

What is meant by the maximum density of a vapor ? What ef- 
fect has severe pressure on certain gases ? Give examples. Can all 
gases be liquefied ? 



BOILING. 53 

LECTURE XI. 

Ebullition. — Theory of Boiling. — In a close Vessel 
Water never Boils. — Effect of Air in Boiling Water. 
— Instantaneous Condensation of Water. — Variabil- 
ity of the Boiling Point. — Effect of Pressure. — Ef- 
fect of the Nature of the Vessel. — Saline Solutions. 
— Boiling on Mountains. — Spheroidal State of Li- 
quids. — Freezing in a red-hot Vessel. 

By introducing different liquids into a tube arranged 
as represented in Fig. 35, we can prove that as soon as 
the boiling point of a liquid is reached, the elastic force 
of the vajDor rising from it is equal to the pressure of 
the air. At a temperature of 80°, vapor of water will 
depress the mercurial column of a barometer about one 
inch ; but if the temperature be raised to 212°, the mer- 
cury is at once depressed to the level in the cistern. 

On these principles, the phenomena of boiling, or ebul- 
lition, are easily explained. When the temperature of 
a liquid is raised sufficiently high, vapor is rapidly gen- 
erated from those portions of the mass which are hot- 
test, and the violent motion characterized by the term 
boiling is the result. This is due to the fact that the 
elastic force of the generated vapor at that point is 
equal to the atmospheric pressure, and the vapor bub- 
bles expanding can maintain themselves in the liquid 
without being crushed in ; they rise to the surface, and 
there burst. But, just before ebullition takes place, a 
singing sound is often heard, due to the partial forma- 
tion of bubbles, which, so long as they are in the neigh- 
borhood of the hottest part, have elasticity enough to 
maintain their form; but the moment they attempt to 
rise through the cooler portion of the liquid just above, 
their elasticity is diminished by their decline of temper- 
ature, and, the atmospheric pressure crushing them in, 
they resume the liquid condition. For a few moments, 

What is the elastic force of a vapor at the boiling point? What 
is the elastic force of vapor of water at 80° and at 212° ? Describe 
the phenomena of boiling. What is the singing sound previous to 
ebullition due to? 



54 



PHENOMENA OF BOILING. 



then, while the vapor has not gathered elastic force 
enough to maintain its condition perfectly, these bub- 
bles are transiently formed and disappear, and the liquid 
is thrown into a vibratory movement, which gives rise 
to the singing sound. 

Water, when heated in a vessel from which the steam 
can not escape, never boils. This takes place in the in- 
terior of Papin's Digester, a strong metallic vessel in 
which -water is inclosed, and the orifice through which 
it was introduced fastened up. As the steam can not 
escape, the water can not boil, no matter what the tem- 
perature may be ; but the vapor accumulating in the 
interior of the vessel exerts an enormous pressure. It 
is under the same conditions as were considered in the 
case of candle-bombs. Papin's Digester is used to effect 
the solution in water of bodies which are not acted on 
readily by that liquid at its common boiling point. 

The presence of air assists the boiling of water ; in- 
deed, pure water can not boil at all. When the air is 
nearly expelled by heating in vacuo, the temperature 
will rise to 360° in an open vessel : a sudden burst of 
vapor will then often shatter it. Slowly -frozen ice, 
heated under oil, acts in the same manner. When a 
liquid has but little adhesion to air, as in the case of 
sulphuric acid, a bumping or irregular boiling is seen. 
As a vapor rising from a vaporizing fluid will bear 
Fig.dQ. no increase of pressure, so neither 

will it bear any reduction of temper- 
ature without instantaneously con- 
densing. This may be strikingly 
shown by an arrangement such as is 
represented in Fig. 36. Into the 
mouth of a flask, a, let there be fitted 
a tube, &, half an inch in diameter, 
bent as in the figure. Having intro- 
duced a little water into the flask, 
cause it to boil rapidly by the ap- 
plication of a spirit-lamp. The steam which forms soon 

What results in heating water in a close vessel ? Describe Papin's 
Digester. Why does not the water in it boil? What effect has the 
air in water on boiling? What is the effect on steam of reduction 
of temperature? How is this shown by the instrument represented 
in Fig. 36? 




CONDENSATION OF VAPOR. 



55 



Fig. ST. 



drives the atmospheric air from the flask and tube ; and 
when this is entirely completed, and the vapor issues 
abundantly from the mouth of the tube, plunge the end 
of the tube beneath some cold water contained in the 
jar c, and take away the lamp. As soon as this is done, 
the cold water, condensing the steam in the tube, rises 
to occupy its place, and presently passing over the bend, 
introduces itself with surprising violence into the inte- 
rior of the flask, filling it entirely full, or, which more 
commonly takes place, breaking it to pieces with the 
force of the shock. The low-pressure engine depends 
on this fact of the rapid condensibility of vapor ; the 
high-pressure engine, on its elastic force. 

The principle involved in the action of 
the low-pressure engine, and more especial- 
ly that form which was the invention of 
ISTewcornen, is well illustrated by the in- 
strument Fig. 37. It consists of a glass 
tube, blown into a bulb at its lower ex- 
tremity. In the bulb some water is placed, 
and a piston slides without leakage in the 
tube. On holding the bulb in the flame 
of a spirit-lamp, steam is generated, and 
the piston forced upward. On dipping it 
in a basin of cold water, the steam con- 
denses, 'and the piston is depressed, and 
this action may be repeated at pleasure. 

As the pressure of the atmosphere de- 
termines the boiling point of a liquid, and as that press- 
ure is variable, the boiling point is not fixed, but is va- 
riable. If a glass of warm water be placed beneath the 
receiver of an air-pump, when the rarefaction has reach- 
ed a certain point ebullition sets in, and the water con- 
tinues to boil at a lower temperature as the exhaustion 
is more perfect. In a vacuum, water can be made to 
boil at 32°, 

On this principle, that the boiling point depends on 
the existing pressure, we find an explanation of a cu- 

What effect is produced by the rapidity of condensation ? On 
what property of vapor does the low-pressure engine depend? On 
what the high-pressure? Describe the instrument Fig. 37. What 
effect has rarefaction of the air on the boiling point ? At what tem- 
perature may water boil in a vacuum ? 




56 VARIATIONS IN THE BOILING POINT. 

rious experiment, called the culinary paradox, in which 
Fig. 3s. ebullition is apparently brought about by 

tthe application of cold. Take a flask, a, 
Fig. 38, and, having filled it half full of wa- 
ter, cause the water to boil violently so as 
to expel the atmospheric air ; introduce a 
c<*rk which will fit the mouth of the flask 
air-tight a moment after it is moved from 
the lamp, and before any atmospheric air 
has been introduced. If the flask be now dipped into a 
jar, 5, of cold water, its water begins to boil, and will 
continue to do so until the temperature is reduced quite 
low. This phenomenon is due to the fact, that the cold 
water condenses the steam in the flask, and a partial 
vacuum is the result. In this partial vacuum the water 
boils, and the steam, as fast as it is generated, is con- 
densed by the cold sides of the flask. 

Besides this variation of the boiling point under va- 
riation of pressure, the nature of the vessel in which the 
process is carried forward exerts a certain action ; thus, 
in a jDolished glass vessel the boiling point is 214°, but 
if a pinch of metallic filings be put in, it falls to 212° ; 
in a rough metal vessel it is 212°. If the glass has been 
carefully cleaned with hot sulphuric acid, water may be 
heated to 221°, and then boiling takes place with bursts 
of steam, the temperature each time falling to 212°. The 
presence of oil elevates the boiling point three or four 
degrees. 

The solution of a salt in water elevates the boiling 
point by the influence of adhesion, and more in propor- 
tion as the amount of salt is larger. A saturated solu- 
tion of chloride of calcium boils at 355°, of acetate of 
potassa at 336°, of nitrate of lime at 304°, of common 
salt at 227°. In certain mountainous regions meat can 
not be cooked by the ordinary process of boiling. As 
we ascend to elevated regions in the air, the atmospher- 
ic pressure becomes less, because the column of air above 
is shorter, and therefore there is less air to press. Un- 
der such circumstances, the boiling point of water, of 
course, descends, and may become so low as not to bring 

Describe the culinary paradox. What effect has the nature of 
the vessel on the boiling point? What effect has the presence of 
salt ? Why is it impossible to cook meat on high mountains ? 




THE SPHEROIDAL STATE. 57 

about the specific change required in the cooking of 
meat. An ascent of 596 feet lowers the boiling point 
one degree. Upon this principle we can determine the 
altitude of accessible elevations, by determining the 
thermometric point at which water boils upon them. 
A peculiar thermometer, the bypsometer, has been in- 
vented for this purpose. ' 

When a drop of water is placed on a red-hot polished 
metallic surface, it does 
not, as might be expect- 
ed, commence to boil rap- 
idly, but remains perfect- 
ly quiescent, gathering it- 
self up into a globule. In 
Fig. 39, JB represents a 
heated metallic basin, 
turned upside down, and 
slightly indented at the 
bottom, so as to permit a 
drop of a mixture of ink and alcohol, <#, to rest there. 
If the metal be now allowed to cool, by withdrawing 
the spirit-lamp as soon as its temperature has reached 
a certain point, the drop is suddenly dissipated in a burst 
of vapor. The temperature to which it is necessary to 
heat the metal varies with the liquid employed, being 
lower tis the boiling point is lower, and as the latent 
heat is less. Water requires at least 340°; alcohol, 
273°; ether, 142°. The liquid remains from 5° to 7° 
below its boiling point. The explanation of this phe- 
nomenon, which is called the spheroidal state of a liquid, 
is that, at the high temperature, the drop is not in con- 
tact with the red-hot surface, but a cushion of steam in- 
tervenes. By bringing the eye to the level of the bot- 
tom of the drop, a bright object beyond may be seen 
through the interval. The steam, being a bad conduct- 
or, prevents ebullition from occurring ; but, as soon as 
the temperature declines and this steam no longer props 
up the drop, an explosive ebullition ensues, because of 
the contact which has taken place. The hand can be 

What number of feet must we ascend to lower the boiling point 
one degree ? How may the heights of mountains be determined on 
this principle? Describe what is meant by the spheroidal state of 
liquids. What is the explanation of this condition ? 

C2 



58 THE BOILING POINT. 

passed through molten cast-iron, in consequence of the 
want of actual contact between the skin and metal, ow- 
ing to the vaporization from its moist surface. If liquid 
sulphurous acid be brought into the spheroidal condi- 
tion in a red-hot platinum capsule, and water dropped 
upon it, ice will be instantly formed. 



LECTURE XII. 

Vaporization. — The Boiling Point rises toith the 
Pressure. — Relation between Insensible and Sensible 
Seat. — The Cryophorus. — Freezing Water in Vacuo. 
— Freezing by Evaporation. — Variability of Moist- 
are in the Air. — Hygrometers : Saussure's, Darnell's, 
the Wet Bulb. — Drying of Gases. 

Under an increase of pressure the boiling point rises, 
and the elastic force of the steam evolved becomes 
greater. As we have seen, the elastic force of steam 
from water boiling at 212° is equal to the pressure of 
one atmosphere. If the pressure be doubled, the boil- 
ing point rises to 250°; if quadrupled, to 291°, and un- 
der a jn-essure of fifty atmospheres, it is 510°. 

These results may be established by the aid of the 
Fig. 40. boiler, a, represented in Fig. 40. It is a 

globular vessel of brass, about three 
inches in diameter. In its upper part 
are three perforations, into one of which 
the stopcock, 5, is secured; through the 
second a tube, c, is inserted, deep enough 
to reach nearly to the bottom of the boil- 
er, and through the third a thermometer, 
c7, is introduced. Some quicksilver is 
poured in, sufficient to cover the end of 
the tube, e, half an inch or more deep, 
and upon it water is poured, the bulb of 
the thermometer being immersed in it. The stopcock, 
#, being open, a spirit-lamp is applied to bring the wa- 
ter to its boiling point, and as the steam can freely pass 

How may ice be formed in a red-hot vessel ? What effect has in- 
creased pressure on the boiling point of water ?, Describe Fig. 40, 
and its method of action. 




LATENT HEAT OF VAPOES. 59 

out, this, of course, takes place at 212°. On closing the 
stopcock the steam can no longer escape, but, exerting 
its elastic force on the surface of the boiling liquid, 
presses the mercury up the tube, c. The altitude of 
the mercurial column measures the amount of this press- 
ure, and the thermometer indicates the corresponding 
change in the boiling point ; as soon as the pressure is 
equal to two atmospheres the thermometer will be 
found to have risen to 250°. 

It is immaterial at what temperature vaporization is 
carried on, a very large amount of heat must always be 
rendered latent ; and, in point of fact, vapors generated 
at a low temperature contain more latent heat than 
those generated at a high one. The relation which ex- 
ists in the amount of heat rendered latent at different 
temperatures is, according to Watt, very simple. The 
sum of the insensible and sensible heat is always the 
same ; thus, water boiling at 212° absorbs 966°, the sum 
being 1178°; but vapor from water at 32° contains 
1146°, the sum again being 1178°. But Eegnault has 
shown that, although in practice the rule works well, 
yet that it is not strictly correct, the latent heat not de- 
creasing as fast as the sensible heat increases. At 8 
atmospheres the sum of the two is 1216°, instead of 
1178°, the boiling point being 340°. 

The increase of elasticity by equal additions of heat 
is greater at high than at low temperatures, and this 
renders the employment of high-pressure engines more 
economical. But it is only when in contact with water 
that this increase is seen ; dry steam follows the general 
law of gases. 

When vapors return to the liquid condition, the heat 
which has been latent in them reassumes the sensible 
form. They may thus be regarded as containing a great 
store of heat, of the effect of which many natural phe- 
nomena furnish us with examples. Thus, there is a re- 
markable difference between the climate of the eastern 
coast of America and the opposite European coasts in 

What is the boiling point under a pressure of two atmospheres? 
"What is the relation between the amounts of latent heat at different 
temperatures of vaporization ? Does the elasticity of vapors increase 
with regularity ? When vapors liquefy, what becomes of their latent 
heat? 



60 THE CRYOPHORUS. 

the same latitude, and this arises from the action of the 
Gulf Stream — a great stream of warm water, which, is- 
suing from the Gulf of Mexico, and passing the Atlan- 
tic States, stretches across toward the European conti- 
nent. The vapors which arise from it give forth their 
latent heat to the air, and the southwest winds, which 
are therefore damp and warm, moderate the climates of 
those countries. 

The cryophorus, or frost-bearer, invented by Wollas- 
ton, in which water may be frozen by the cold produced 
by its own evaporation, depends for its action on the 
laws relating to latent heat. It is represented in Fig. 
41, and consists of a bent tube half an inch or more in 

Fig. 41. 



diameter, with a bulb at each extremity ; the left-hand 
bulb is filled one half with water, and the rest of the 
space, w T ith the tube and the other bulb, is filled with 
the vapor of water only. If now the right-hand bulb be 
immersed in a freezing mixture of nitric acid and snow, 
although the tube may be of considerable length, the 
water in the distant bulb presently freezes; hence the 
name of the instrument, frost-bearer, because cold ap- 
plied at one point produces a freezing effect at another 
which is at a distance. The action is simple : in the 
cold bulb, which is in contact with the freezing mix- 
ture, the vapor is condensed, fresh quantities rise with 
rapidity from the water in the other bulb, to be in their 
turn condensed; a continual condensation therefore 
goes on in the one, and a continual evaporation in the 
other, but the vapor thus formed must have heat of elas- 
ticity ; it obtains it from the water from which it is ris- 
ing, the temperature of which, therefore, descends until 
solidification takes place. 

What effect has the Gulf Stream on the climate of Europe ? De- 
scribe the construction of the cryophorus. What is the principle 
of its action ? 



EVAPORATION PRODUCES COLD. 




Leslie's process for freezing water in vacuo by its 
own evaporation is an example of the same kind. If 
some water in a watch-glass be placed in an exhausted 
receiver, with a large surface of sulphuric acid, as fast 
as vapor rises it is condensed by the acid, a rapid evap- 
oration of the water 
therefore takes place, F?g. 42. 

the temperature falls, 
and congelation en- 
sues. In Fig. 42 this 
apparatus is represent- 
ed. T is the watch- 
glass, containing wa- 
ter; #, a wide dish, 
filled with sulphuric 
acid, and i 3 , a l<$w bell- 
jar, in which the ex- 
haustion is made. 

A drop of prussic acid held in the air on the tip of a 
rod solidifies, the portion that evaporates obtaining its 
latent heat from the portion left behind ; and on the 
same principle liquid carbonic acid can also be solidified. 
If a drop of water be placed between two watch-glasses, 
and a little ether poured into the upper one, on putting 
it under an exhausted receiver the ether will boil, and 
the two glasses freeze together. 

The pulse-glass is an instrument which serves to il- 
lustrate the fact that evaporation is a cooling process. 
It consists of a glass tube bent twice at right angles, 
and terminated by bulbs, as 
in Fig, 43, It is partially 
filled with alcohol, the rest 
being occupied by vapor of 
that substance. On grasp- 
ing one of the bulbs in the hand, the warmth is sufficient 
to boil the liquid, and as it distils over into the other 
bulb an impression of cold is felt. 

The amount of watery vapor contained in the air is 
very variable. Many common facts prove this. The 
swelling of wooden furniture takes place in consequence 

Describe Leslie's process for freezing water. Why docs liquid 
prussic acid solidify when exposed to the air? How may water be 
frozen by the aid of ether ? Describe the pulse-glass. 



Fig. 43 




62 



HYGROMETERS. 




of damp weather, and the opposite effect, or its shrink- 
ing, occurs during dry. Several instruments have been 
invented to determine what the amount is at any time; 
they are called hygrometers. 

Saussure's hygrometer consists of a human hair 8 or 
Fig.u. 10 inches long, b c, Fig. 44, fastened at one 
end to a screw, a, and at the other passing 
over a pully, c, being strained tight by a silk 
thread and weight, d. From the pully there 
goes an index, which plays over the graduated 
scale, e e\ so that as the pully turns through 
the shortening or lengthening of the hair the 
index moves. The instrument is graduated 
to correspond with others by first placing it 
under a bell-jar, with a dish of sulphuric acid, 
or other substance having an affinity for wa- 
ter, which, absorbing all the moisture of the 
air of the bell, brings it to absolute dryness. The 
point at which the index then stands is marked 0°. The 
hygrometer is next placed in ajar, the interior of which 
is moistened with water ; when the index has again be- 
come stationary the point is marked 100°, and the in- 
tervening space divided into 100 equal parts. The hair 
should have its oily matter removed by soaking in sul- 
phuric ether. This renders it more sensitive. 

There is a simple and ingenious instrument, the move- 
ments of which depend on these principles : it is repre- 
Figt 45 sented in Fig. 45. A thin slip of 

pine wood, aa, cut across the grain, 
a foot long and an inch wide, has 
inserted into its corners four nee- 
dles, all pointing in one direction backward. If this in- 
strument be set upon a floor or flat table, in the course 
of time it will crawl a considerable distance. During 
dry weather the thin board contracts, and the two fore 
legs taking hold of the table, the hind ones are drawn 
up a little space; when the weather turns damp the 
board expands, and now the hind legs, pressing against 
the table, cause the fore ones to advance. Every change 
from dry to damp, or the reverse, produces a walking 

What is a hygrometer? Describe Saussure's hygrometer. How 
is Saussure's hydrometer graduated ? What is the construction of 
the instrument Fig. 45 ? Describe its method of action. 



4" 



* 



DANIELI/S HYGROMETER. 



63 



Fig. 46. 



motion in a continuous direction, and the distance pass- 
ed over is a register of the sum total of all these changes. 

But, of all hygrometric methods, the process known 
as " the determination of the dew point" is the most 
philosophical. This method consists in cooling the air 
until it begins to deposit moisture. When there is 
much moisture in the air, it obviously requires but a 
slight diminution of the temperature to cause a portion 
of the vapor to deposit as a dew ; but when the air is 
dryer, the cooling must be carried to a greater extent. 
The precise thermometric point at which the moisture 
begins to deposit is called the dew point. 

Daniell's hygrometer affords a ready and beautiful 
method of determining 
the dew point. It con- 
sists of a cryophorus, 
a c 5, Fig. 46, the bulb b 
being made of black 
glass, and a covered 
over with muslin. The 
bulb b contains ether in- 
stead of water, and into 
it there dips a very del- 
icate thermometer, cL 
Usually another ther- 
mometer is affixed to 
the stand of the instru- 
ment. When a little 
ether is poured on a, by 
its evaporation it cools 
that bulb 5 and ether dis- 
tils over from 5, which, 
of course, becomes cold. After a time the temperature 
of b sinks to the dew point, and that bulb becomes cov- 
ered with a dew. The thermometer, c?, then shows at 
what temperature this takes place, and of course gives 
the dew point. Knowing the temperature of the air, 
the dew point, and the barometric pressure, the abso- 
lute amount of vapor can be determined by calculation. 

The amount of evaporation, and its great variation at 




What is meant by determination of the dew point? Describe 
Daniell's hygrometer. How is it used ? 



64 



THE AVET BULB HYGROMETER. 



different seasons of the year, is shown by the following 

table : 



Mean Temperature. 


Mean Dew 
Point. 


Maximum Evaporation in 
24 hours. 


Annual 49°.8S 

Summer 62°.21 

Winter 38°.95 


44°. 31 
54°. 56 
35°.64 


7,166 galls, per acre 
15,048 " " 
3,450 " 



Fig. 47. 




The wet bulb hygrometer con- 
sists of two mercurial thermom- 
eters, S S, which exactly corre- 
spond. The bulb of one of them, 
&, Fig. 47, is covered with muslin, 
and kept constantly wet by water 
supplied from a reservoir, A c, 
by capillary attraction along a 
thread, e. The other bulb is cov- 
ered with dry muslin. Owing 
to the evaporation from the wet 
bulb, its temperature will be low- 
er than the dry one, and this in 
proportion to the rate of evapora- 
tion or the dryness of the adja- 
cent air. My is the supporting 
stand. If both thermometers, the 
wet and the dry, coincide, the air 
contains moisture at its maximum 
density, and the greater the dif- 
ference between them, the dryer 
the air. In practice it is found 
that this instrument requires a va- 
riety of corrections to ascertain 
the dew point, the difference be- 
tween the two thermometers be- 
ing multiplied by a number which 
varies with the actual tempera- 
ture. 

It is frequently necessary to re- 
move moisture from air or gases. 
This may be done by conducting 
them through tubes containing 



Describe the wet bulb hygrometer. What is its principle of ac- 
tion ? How may £ases be freed from moisture? 



SPECIFIC GRAVITY OF VAPOES. 



65 



bodies having a strong attraction for water, such as 
chloride of calcium, sulphuric or phosphoric acids. Such 
an arrangement is shown in Fig. 48, in which A is the 




bottle in which the gas is generated ; B, a bent tube 
filled with chloride of calcium ; D, a bulb containing 
material on which the dried gas is to act; and C C, 
caoutchouc connecting pieces. 



LECTURE XIII. 

Evaporation and Interstitial Radiation.— -Dumas' s 
Method of ascertaining the Specific Gravity of Va- 
pors. — Rapidity of Evaporation. — Control of Tem- 
perature, Dryness, Stillness, Pressure, and Surface. 
— Limit of Evaporation. — Conduction of Solids* — 
Difference among Metals. — Effect of Wire- Gauze on 
Flame. — Explanation on the Dynamical Theory of 
Heat. — RumfonTs Experiments on Clothing. 

The specific gravity of vapors may be determined in 
several ways. The method of Dumas consists in weigh- 
ing a glass globe filled with the vapor to be tried. A 
portion of the substance is to be introduced into the 
globe, A, Fig. 49, the weight of which is first determ- 
ined, and this is then held, as shown in the figure, by 
a handle, C, in a bath of fusible metal, placed over a 
small furnace. The heat of the melted metal vaporizes 

Describe the apparatus Fig. 48. Describe Dumas's method of 
determining the specific gravity of vapors. 



66 



SPECIFIC GRAVITY OF VAPORS. 




the substance, drives out the 
air, and occupies the whole 
cavity in a state of purity. 
When no more vapor escapes 
from the end of the tube, 5, it 
is sealed by the blowpipe, and 
the temperature of the bath 
ascertained by the thermome- 
ter, I. The globe is now to be 
carefully weighed, when cold, 
a second time, and the point 
of the tube is then broken un- 
der quicksilver, wmich rises, 
and fills it completely ; and 
this being subsequently emp- 
tied into a graduated jar, the 
volume of the globe is ascer- 
tained. Knowing the volume 
of the globe, Ave .know the 
weight of the air it contains, 
and this, subtracted from the first weight, is the weight 
of the glass when empty. Subtracting this again from 
the second weighing gives us the weight of the vapor; 
and, as the air and vapor occupied the same volume, 
their densities are as their weights. But as their tem- 
perature was different, a farther calculation is required 
to bring them to the same standard. 

There are several conditions which exert a control 
over the rapidity of evaporation. The amount of vapor 
which can exist in a given space depends entirely on 
the temperature. Thus, the air included in a glass jar 
which is standing over water contains at 32° a certain 
quantity of vapor, but if the temperature rises to 60° it 
contains more, and still more at 90°. Should the tem- 
perature descend, a part of the vapor is deposited as a 
mist. 

It is the application of this principle which consti- 
tutes the most beautiful part of Watt's great invention, 
the low-pressure steam-engine. Taking advantage of 
the fact that the quantity of vapor which can exist in a 
given space is determined by the lowness of the tem- 

What conditions determine the rate of evaporation? What im- 
provement did Watt make in the steam-engine? 



CAUSES CONTROLLING EVAPORATION. 67 

perature of any portion of it, he arranged a vessel main- 
tained uniformly at a low temperature, in connection 
with the cylinder of the engine, and thus condensed the 
steam without cooling the cylinder. Previous to his 
time a jet of water had been thrown directly into the 
cylinder, and its whole mass cooled — a slow operation, 
and one which involved raising the whole mass again to 
the heat of the incoming steam before the piston could 
be forced up once more. 

Among other causes exerting a control over evapo- 
ration into the air is the dry or damp state of that me- 
dium. As is well known, evaporation goe.s on with 
rapidity when the weather is dry, and is greatly retard- 
ed when the weather is damp. So, too, a movement or 
current exerts a great effect. When the wind is blow- 
ing water will evaporate much more quickly than when 
the air is quite calm. This obviously depends on a con- 
stant renewal of surface, so that as fast as one portion 
of air becomes moist it is removed, and a dryer portion 
takes its place. Extent of surface operates in the same 
way. The same quantity of water will evaporate much 
more rapidly if exposed in a plate than if exposed in a 
cup. Pressure also exerts a great control; for, as we 
have seen, evaporation takes place instantaneously in a 
vacuum. But while there are several circumstances 
which control the rate of evaporation, it is temperature 
alone which regulates the absolute and final amount. 

At one time it was supposed that evaporation was 
due to a solvent power in the air, a kind of attraction 
between that medium and the water with which it was 
in contact ; but such an opinion is wholly untenable, for 
the process goes on with the greatest rapidity in a vac- 
uum when the air is totally removed. 

Although the evaporation of liquids, such as water, 
will take place at very low temperatures, there is reason 
to believe that the process has a limit ; thus, a minute 
quantity of vapor will rise from quicksilver at a tem- 
perature of 60°, but at 40° not a trace can be discovered. 

What was the disadvantage of the method previously used ? 
What effect has dryness of the air on evaporation ? What effect 
have currents? What other circumstances influence the rate of 
evaporation? What was evaporation formerly supposed to he due 
to ? Is there a temperature below which evaporation ceases ? 



68 CONDUCTION. 

Sulphuric acid does not evaporate at all at ordinary 
temperatures. The cohesion of the liquid overcomes 
the evaporating tendency. 

Interstitial Radiation or Conduction. 

It is commonly said that heat is transmitted through 
bodies by conduction, a term which involves the idea 
that the particles are in contact, whereas it has been 
proved that they are separated by interspaces. The 
passage of heat across these interstices is called inter- 
stitial radiation. From the convenience of the expres- 
sion, the term conduction will be frequently used. 

Different solids conduct heat with different degrees 
of facility. If we take a cylindrical mass of metal, and 
hold tightly against its surface a piece of white writing 
paper, the paper may be placed in the flame of a spirit- 
lamp for a considerable time without scorching ; but if 
we take a cylindrical piece of wood of the same dimen- 
sions, and, wrapping the paper round it, expose it to 
the flame, it rapidly scorches. The metal, therefore, 
keeps the paper cool by carrying off the heat, but the 
wood, being a bad conductor, suffers the paper to burn. 
By the aid of the apparatus of Ingenhausz, Fig. 50, 
Fig. so. the same fact can be proved in a more 

tf\ general way. It consists of a trough of 

qjs&^n^,,,^! brass, 6 inches or more long, 3 wide, and 
^PP^J 3 deep ; from the front of it project cylin- 
I I I I I ders of metallic and other substances, of 
the same length and diameter. They may be of silver, 
copper, brass, iron, porcelain, wood, etc., in succession. 
The surface of each cylinder is smeared with beeswax. 
On pouring boiling water into the trough, the heat 
passes along these cylinders with a rapidity correspond- 
ing to their conducting power, and the wax correspond- 
ingly melts. On the silver bar the wax melts most 
rapidly, and on the wood most slowly ; on the others 
intermediately: thus affording a clear proof that differ- 
ent solids conduct heat with different degrees of facility. 
The actual conducting power is in this experiment corn- 
Why is the term conduction erroneous? Do all solids conduct 
alike? Describe the experiment with a cylinder of wood, and one 
of metal. Describe the apparatus of Ingenhausz. What does it 
prove ? 



rr 



CONDUCTION OF HEAT. 69 

plicated with the specific heat of the substance, that 
having a low specific heat seeming to conduct more 
rapidly. It is only necessary, in order to correct this 
source of error, to wait a certain length of time, and ob- 
serve the distance to which the melting takes place. 
The apparatus Fig. 51 demonstrates the same fact. 







w w 



It consists of two similar bars of metal, B C, placed 
end to end ; one may be of copper, the other of iron. 
To their under sides a number of balls of wood are at- 
tached by wax. On heating the junction A, the power 
of conduction is seen to differ, from the fact that, on 
the copper, the balls drop off to a greater distance from 
the source of heat than on the iron. 

The instrument Fig. 52 can be made to exhibit to a 
number of persons differences in p . 52 

conducting power. From a cen- 
tral ring of brass a number of 
arms of, various substances, as 
copper, brass, iron, porcelain, etc., 
project radially. On the tip of 
each arm is a piece of phospho- 
rus. When the ring is held by 
the aid of the handle in the flame 
of a spirit-lamp, so that the flame passes through the 
central aperture, it will be found that the pieces of 
phosphorus inflame one after another, and not simulta- 
neously. That on the copper takes fire first, the brass 
next, etc., the order being the same as that shown by 
Ingenhausz's apparatus. 

Describe Fig. 51. What is the construction and mode of "action 
of Fig. 52 ? 




70 



CONDUCTING POWER OF METALS. 



Table of the Conducting Power 


of Solids. 




For Electricity. 


For Heat. 


Silver 


100 
73 
59 
22 
23 
13 
11 
10 
6 
2 


100 

74 

53 

24 

15 

12 

9 

8 

6 

2 


Copper 


Gold 

Brass. 


Tin 


1 Iron 


Lead 


Platinum 


German Silver 

Bismuth 





The purity of the metals is of importance. Gold, 
•when alloyed with 1 per cent, of silver, loses 20 per 
cent, of its conducting power. Some alloys conduct in 
the ratio of the mean of the two metals; some no bet- 
ter than the inferior metal. Carbon diminishes the 
conductivity of iron ; malleable iron, steel, and cast iron 
being as 44 to 40 to 36. 

If a piece of wire gauze be held over the flame of a 
candle or gas-jet, Fig. 53, the flame 
falls to pass through ; but the gaseous 
matter of which the flame consists 
freely escapes through no. u. 

the meshes of the 
gauze, and may be set 
on fire above it, as in 
Fig. 54. Flame is ei- 
ther gaseous matter 
or solid matter in a state of minute 
subdivision, temporarily suspended in 
gas brought to a very high tempera- 
ture. It can not, therefore, pass through 
a piece of wire gauze, because the me- 
tallic threads, exerting a high conducting power, ab- 
stract its heat from the incandescent gas, and bring its 
temperature down to a point at which it ceases to be 
luminous. The safety-lamp of Davy is an application 
of this principle ; by it combustion is prevented from 

Give the order of conducting power among metals. What effect 
has the purity of a metal on its conducting power? What effect is 
seen on holding wire gauze over the flame of a lamp ? How may 
we show that the combustible matter passes through ? 





CONDUCTION OF SOLIDS. 



71 



spreading through masses of explosive gas by Firj - 55 - 
calling into action the conducting power of 
metallic gauze with which the lamp-flame is 
surrounded, as in Fig. 55. Hemmings's safe- 
ty-tube, used to prevent explosions in the oxy- 
hyclrogen blowpipe, acts on the same princi- 
ple. The action of gauze is explained gn the 
dynamical theory of heat, as follows: in a 
flame, the molecular movement is very in- 
tense, but the weight of the moving particles 
is but small. If their motion be communica- 
ted to a heavy body, the intensity of the mo- 
tion must fall, just as a light bullet shot from 
a, rifle could communicate to a 100-pound 
cannon-ball but a low velocity of motion. In 
placing a gauze over a flame, the intensity of motion is 
so much reduced that it is unable to propagate the 
combustion to the opposite side of the gauze. 

Count Rumford made several experiments to determ- 
ine the conducting power of the materials that are used 
for clothing. He placed the bulb of a thermometer in 
the centre of a glass globe of large diameter, and filled 
the interspace with the substance to be tried. Having 
immersed the apparatus in boiling water until it was at 
212°, he transferred it to a freezing mixture, and ascer- 
tained how many seconds it took to cool 135°. Lin- 
en and cotton were found to be better conductors than 
wool and the various furs, and hence the reason that 
they are preferred as articles of summer clothing. The 
greatest impediment to the transmission of heat was 
offered by hare's fur and eider down. The state of 
compression also influences the result, raw silk taking 
1264 seconds to cool the specified amount, while twist- 
ed silk only took 917. Such bodies act not so much by 
their own bad conducting power as by calling into ac- 
tion the non-conducting quality of air. 

Only those crystalline bodies which belong to the 
regular system conduct equally in all directions. If 

How is Davy's lamp constructed? How is the action of gauze 
explained on the dynamical theory of heat? What was the object 
of Rumford's experiments? How were they conducted? What 
are the worst conductors of heat, among solid bodies? What is the 
reason of their resistance to conduction ? 



72 



CONDUCTION OF LIQUIDS. 



Fig. 56. 




two plates be cut from a rhombohedral 
crystal, as a prism of quartz, one par- 
allel to the axis, the other at right an- 
gles to it, and these be warmed from a 
point at the centre by the aid of a sil- 
ver wire, if the plates have been coat- 
,ed previously with wax, it will be seen 
that the first plate, 2, Fig. 56, shows 
an elliptical spot of melting, while the 
other, 1, shows a circle, and demon- 
strates an equal rapidity of conduction 
in all directions. When a substance 
is altered by unequal tension, as in the 
case of a plate of unannealed glass, 
heat is conducted most slowly in the 
line of greatest density or pressure. 
Wood also shows similar differences 
of conduction in different directions. 



LECTURE XIV. 

Conduction. — Conduction of Liquids. — Convection, 
or Heating by Circulation. — Conduction of Gases. 
— The Trade- Winds. — Land and Sea Breezes. — Ap- 
plications of the Mon-conducting Power of Air. 

The conducting power of most liquids, such as water, 
is very low ; a thin stratum is sufficient almost entirely 
to cut off the passage of heat. This may be shown by 
the apparatus Fig. 57, consisting of a funnel partly fill- 
ed with water, with an air-thermometer included in 
such a manner that the bulb is within a short distance 
of the surface, a depth of a quarter of an inch or less in- 
tervening. The tube of the thermometer may be pass- 
ed through the lower mouth of the funnel, water-tight 
by means of a cork, and the position at which the index- 
liquid stands having been marked, some ether is poured 
on the surface of the water, upon which it readily floats, 
and set on fire. A voluminous flame is the result, and 

Do solids conduct equally in all directions ? Describe Fig. 56. 
What effect has pressure on conduction? How does the conducting 
power of liquids compare with that of solids ? Describe Fig. 57. 



CONVECTION. 



IS 




a great deal of heat is evolved ; and since the bulb of 
the thermometer is apparently sep- ^ 5T 

arated from the flame by a thin film 
of water only, if the heat traversed 
that film the thermometer should 
rapidly move, but it does not ; we 
therefore conclude that water is a 
very bad conductor of heat. 

But the experiment is very de- 
ceptive ; for as the flame is hollow, 
and only incandescent on its sur- 
face, it is really a great distance 
from the thermometer bulb, and, 
in addition, the evaporation of the 
ether is a cooling operation. The 
conclusion is nevertheless true. 

To a certain extent all liquids 
conduct. Mercury is a good conductor ; but, in those 
of which water is the type, the dissemination is chiefly 
effected by a process called convection or circulation, 
which depends on the free mobility of their particles. * 

The apparatus Fig. 58 illustrates this process. It con- 
sists of a wide tube, into Avhich the water pig, 53. 
may be poured ; the lower portion as high 
as a being colored blue by the addition of 
some coloring substance, the intermediate 
portion from a to b being colorless, and 
the upper portion, from b to c, being tinged 
yellow. By the application of a red-hot 
ring, c?, of such a diameter that it can sur- 
round the jar, a space of an inch or more 
intervening all round, the upper yellow 
portion may be made even to boil, without 
showing any disposition to intermix with 
the portions beneath ; but if the red-riot 
ring is lowered so as to surround the blue portion, as it 
becomes warm it will be found to ascend first through 
the colorless stratum, and finally that tinged yellow on 
the top. When the lower portion of the liquid is warm- 
ed, currents are established, which, rising through the 




Why is this experiment deceptive? Do liquids conduct at all? 
How is heat disseminated in liquids ? Describe Fig. 58. 



D 



74 



PROPAGATION OF HEAT IN LIQUIDS. 




strata above, bring about a rapid dissemination of the 
heat. 

This may also be shown by taking a flask, Fig. 59 y 
Fig. 59. and filling it with water, in which 

some light substance, such as bran, 
is suspended. On applying a lamp 
to the bottom of the jar, currents 
are established in the w T ater, rising 
up the centre and descending down 
the sides of the liquid ; and in this 
manner, new portions constantly 
presenting themselves on the sur- 
face exposed to the flame, the 
whole mass becomes uniformly 
hot. 

The cause of this movement is 
due to the fact that when water is heated it expands. 
Those portions, therefore, which rest on the bottom of 
the vessel, and to which the heat is applied, as soon as 
they become warm dilate, and, being lighter than before, 
rise to the top of the liquid, while colder, and therefore 
heavier ones, occupy their place. 

In the vegetable world, advantage is taken of the non- 
conducting power of water in a very beautiful way. 
Soon after sunset, the leaves and delicate parts of j:>lants 
become covered with little drops of dew, which invest 
them on all sides Under these circumstances, the pro- 
cess of convection, or the establishment of currents, is 
entirely cut off, for each of the drops is isolated and has 
no communication w r ith those around. The cold air 
does not suddenly affect the delicate organs, as it would 
do were not this non-conducting film spread over them ; 
their action is therefore less liable to be deranged. 

All liquids possess true, though in most cases extreme- 
ly feeble powers of conduction, as compared with sol- 
ids. They also vary among themselves. 

If the conducting power of liquids is small, that of 
gaseous bodies is so much less, that it is doubtful wheth- 
er they can be proved to conduct at all. In these the 

How may the currents in liquids be shown? "What is the cause 
of the movement? Describe the formation of dew on plants at 
nightfall. Of what use is the covering of water? Do gases con- 
duct heat ? 



THE TRADE-WINDS. 75 

mobility of particles is so great that heat is readily dif- 
fused through them. On burning sulphur in oxygen 
gas, the establishment of currents is well shown. The 
ventilation of buildings and mines, and the proper con- 
struction of furnaces and chimneys, depend on gaseous 
convection. The trade-winds are an illustration, on a 
grand scale, of the movements of a gas caused by heat. 
The temperature of the earth's surface is greatest in the 
tropics, and the air there expands, rises, and is replaced 
by cooler air flowing in from the polar regions. The 
heated air, after ascending a certain distance, flows over 
and tends to go toward the poles, to take the place of 
the air that has gone to the tropics. If the earth were 
at rest, there would be a steady breeze toward the poles 
in the upper parts of the atmosphere, and one in the op- 
posite direction below ; but, as the globe is revolving 
from west to east at the rate of 1000 miles an hour at 
the equator, and with less rapidity as the poles are ap- 
proached, where the motion vanishes, the direction of 
the flowing streams of air is changed. The equatorial 
air, which has been moving at the same rate as the earth 
below, when it travels toward the poles, moves faster 
than the ground, and the wind has a westerly direction. 
On the contrary, the polar air, going toward the equa- 
tor, drags against the surface of the earth until it has 
acquired the same velocity, and has apparently an east- 
erly direction, which is less and less marked as the equa- 
tor is approached. 

Land and sea breezes are to be explained on the same 
principles. During the day the surface of an island will 
warm faster than the sea around, the air over it will di- 
late, and an inward current, the sea breeze, will be es- 
tablished. At night it cools more quickly, and the air 
over becoming denser, flows out toward the sea, causing 
the land breeze. 

By taking advantage of the non-conducting power 
of air, rooms may be kept warm with a small consump- 
tion of fuel by furnishing them with double windows. 
A stratum of air an inch thick cuts off the loss of heat 

Why does heat diffuse easily through them ? Describe the trade- 
winds. What is the apparent direction of the trade-winds ? Ex- 
plain the cause of land and sea breezes. Upon what principle do 
double windows act? 



76 NATURE OF KADI ANT HEAT. 

through the windows to a great extent. The same fact 
accounts for the difference of conduction in Rumford's 
experiment, when the materials were closety and loose- 
ly packed. In the latter case, the slow conduction is 
due to the entrapped air, in which convection is almost 
entirely prevented by the fibres of the materials. The 
same explanation affords the reason for the warmth of 
the down and fur of animals. 



LECTURE XV. 

Radiation. — Preliminary Ideas on Radiant Heat. — 
Analogies ivith Light. — Effect of Surface on Radia- 
tion. — Relations of Radiation, Reflection, and Ab- 
sorption. — The Florentine Experiment. — The Gold- 
Ray Experiment. — Opacity of Glass to Heat ofLoio 
Refrangibility. — Diathermacy of Different Solids, 
Liquids, Gases, and Vapors. — Action of Perfumes. 
— Heat is an Ethereal Vibration.— MellonV s Appa- 
ratus. 

Though gases are bad conductors of heat, they freely 
allow its transmission by radiation, the solar rays, in 
traversing 6000 feet of air, only losing one fifth of their 
heat. A person who stands at one side of a fire re- 
ceives the heat of it, although no currents of warm air 
can reach him. In a vacuum a piece of red-hot metal 
rapidly cools. 

The heat which under these circumstances escapes 
from bodies is entirely invisible to the eye : it moves in 
straight lines, exhibiting many of the phenomena of the 
rays of light. Thus, if we interpose between a fire and 
thermometer an opaque screen, the moment the rays of 
light are stopped the heat is simultaneously intercepted. 

The rays of heat, like the rays of light, are capable 
of being reflected by polished metallic surfaces. If a 
piece of planished tin be held before a fire in such a po- 
sition as to reflect the light of it upon the face, the heat 
also is similarly reflected, and gives rise to a sensation 
of warmth. 

Do gases transmit radiant heat ? How may it be proved that ra- 
diant heat moves in straight lines ? Is it capable of reflection ? 



VARIATION OF SURFACE RADIATION. 



11 



Fig. 60. 



The analogy between light and heat is still farther 
observed when the rays of the latter fall upon bodies 
of a different physical constitution from the metals. As 
glass is transparent to light, there are many bodies 
transparent to the rays of heat, though, as we shall find, 
these are not the same in both instances ; and as there 
are substances, like lampblack, which will absorb all the 
light which impinges on them, there are many which 
perfectly absorb heat. Reflection, transmission, and ab- 
sorption are therefore common to both these agents. 

If we take two metallic vessels of the same size and 
shape, and, having blackened one of them all over with 
the smoke of a candle, fill them both with hot water 
and notice their rate of cooling, it will be seen that the 
blackened one cools faster : the same thing may be ob- 
served if, instead of blackening the vessel, it is covered 
with layers of varnish. These results may be proved 
by the aid of Leslie's Canister, which consists of a cu- 
bical brass vessel, a, 
Fig. 60, set upon a ver- 
tical stem, upon which 
it can rotate. At a lit- 
tle distance is placed the 
blackened bulb of a dif- 
ferential thermometer, 
d ; a mirror, M, receives 
the rays of the canister 
and reflects them on the thermometer. One of the ver- 
tical sides of the cube is left with a clear metallic sur- 
face, a second washed over with one coat of varnish, a 
third with two, and the fourth w T ith three coats. If 
these sides be presented in succession to the thermom- 
eter, they will be found to radiate heat with very differ- 
ent degrees of speed, more heat escaping from them as 
the number of coats is increased. Melloni found that 
the maximum was not attained until sixteen coats were 
applied. 

These results can only be explained on the principle 
that radiation does not take place from the surface of 

"What farther analogies are there between light and heat ? In 
what manner can the radiating power of a surface be increased ? 
Describe the experiment, Fig. 60. Does radiation take place from 
the surface alone ? 




78 REFLECTION OF RADIANT HEAT. 

bodies merely, but from a certain depth in their in- 
terior. 

A highly polished metal is a bad radiator, but on 
roughening it this quality is improved. As a general 
rule, good radiators are bad reflectors, and good reflect- 
ors are bad radiators. This latter statement is exempli- 
fied in the case of a silver teapot, which retains its heat 
much longer than an unpolished vessel. 

It is important to bear in mind that the absorbing 
and radiating powers of a substance are directly pro- 
portioned to one another. 

When rays of light diverging from the focus of a con- 
cave parabolic mirror impinge on the surface, they are 
reflected in parallel lines ; when parallel rays fall on such 
a surface, they are reflected to its focus. Thus, if from 
the point a, Fig. 61, the focus of a parabolic concave, 
cf, rays diverge, they will be reflected in parallel lines, 
eg, dh,ei,fk / and if at these points they be inter- 
cepted by the mirror, g &, they will be reflected to its 
focus, b. 

Now, as the laws of the reflection of radiant heat are 
the same as the laws of the reflection of light, it is plain 
that if Ave place any incandescent body, such as a red- 
hot cannon-ball, in the focus a, heat which radiates from 
it will be found at the other focus, b. 

This is beautifully illustrated by an experiment known 
under the name of the experiment with the conjugate 
mirrors. In the focus «, Fig. 61, of a parabolic mirror, 
cf, place a red-hot cannon-ball, and in the focus b of a 
second mirror, g k, set opposite, but twenty or thirty feet 
off, place a piece of phosphorus, a screen intervening be- 
tween. As soon as the arrangements are conrpleted, 
remove the screen, and in a moment the phosphorus 
takes fire. That this effect is due to the reflecting ac- 
tion of the mirrors, as has been described, may be proved 
by removing the mirror cjf\ when it will be found that 
the phosphorus can not be lighted, even though the ball 
be brought within a very short distance of it. If the 

What effect on the radiating power is observed on roughening a 
polished surface ? What relation is there between absorbing and ra- 
diating power ? What is the action of a parabolic mirror on paral- 
lel rays ? What is its action on rays diverging from its focus ? De- 
scribe the experiment, Fig. 61. 



FLORENTINE AND COLD RAY EXPERIMENTS. 79 

mirrors are well adjusted, the cannon-ball may be re- 
placed by an ordinary gas flame. 

Fig. 61. 



w\ 



to 



o 



T 




"^ 



This striking experiment proves, first, that the rays* 
of heat move in straight lines, like those of light ; and, 
second, that in the same manner they are subject to the 
ordinary laws of reflection, for the apparatus is adjusted 
by the flame of a candle. 

A variation of the experiment may be made by using 
a snowball, (7, Fig. 62, instead of the heated body, in the 
focus of JVJ in which case a thermometer, J5, in the fo- 

Fin. 62. 




cus of the opposite mirror, M, will exhibit a reduction 
of temperature, even though shaded by a screen, A % 
from direct radiation. From this it was at one time 
supposed that there exist rays of cold precisely anal- 
ogous to rays of heat, and that they observe the same 

What does the experiment of the conjugate mirrors prove ? De- 
scribe the experiment, Fig. 62. What was it supposed to prove ? 



80 OPACITY OF GLASS TO HEAT. 

laws ; but, as we shall see in speaking of the Theory of 
the Exchanges of Heat, a simple explanation can be 
given without implying the existence of a principle of 
cold. 

Let it be supposed that in the focus of the •mirror g Jc^ 
Fig. 61, the bulb of a delicate thermometer is placed, 
and in the focus of the other mirror, cf^ a metalline mass, 
a, the temperature of which can be varied at pleasure. 
Between the mirrors let there be interposed a screen of 
transparent plate glass, and let us farther suppose that 
the temperature of a is 212°, or considerably below the 
point at which it is visibly red-hot. Under these cir- 
cumstances the thermometer exhibits no rise of temper- 
ature sp long as the glass intervenes, but the moment it 
is removed the heat passes. 

A piece of transparent glass is therefore opaque to the 
rays of heat which come from a non-luminous source. 
* Let us now suppose that the temperature of the met- 
alline mass a continually rises. When it has reached a 
red-heat, a certain proportion of the rays emitted by it 
begins to pass through the glass, as is shown by the 
effect upon the thermometer. When the mass is visi- 
bly red-hot in the daylight, the rays go through the 
glass more readily ; and when it has become white-hot, 
or has reached the highest temperature we can give it, 
the glass transmits the rays with facility. 

These facts are of the utmost importance. They 
show that bodies transparent to light are not necessari- 
ly transparent to heat, and, therefore, that there is a 
distinction between the two agents. They farther 
show that, as respects glass, its transparency for heat 
differs with the temperature of the source from which 
the rays come. 

There is only one known solid that approaches per- 
fect transparency for heat, rock salt. If, in the preced- 
ing experiment, a plate of it were substituted for the 
glass, no matter what the temperature of the mass a, 
the rays would pass through it with equal facility. It 
is the glass for heat, and stands at the head of diather- 

What effect lias glass on heat of low intensity? What changes 
occur in the transmissive power of glass as the. temperature rises ? 
What facts are shown by these experiments? What substance is 
transparent to heat ? 



DIATHERMACY OF SUBSTANCES. 81 

mic bodies, as those transparent to heat are called. An 
athermic substance is one which does not permit heat 
to pass. 

Diathermacy of different Solids. 



Eock Salt........ 92.3 per cent. 

Sulphur 74 " 

Iceland Spar.... 39 " 

Plate Glass 39 



Limpid Quartz .... 38 per cent. 
Smoky Quartz.... 37 " 

Alum 9 " 

Ice 6 " 



The plates of the substances used in determining the 
above percentages were one tenth of an inch thick, and 
the source of heat was a naked flame. When copper at 
212° was used, only the rock-salt, sulphur, and quartz 
permitted any rays to pass, the rest being perfectly 
athermic. 

Diathermacy of Liquids. 

Bisulphide of Carbon 63 per cent. 

Chloride of Sulphur 63 

Spirit of Turpentine 31 

Olive Oil 30 

Ether 21 

Sulphuric Acid 17 

Alcohol 15 

Distilled Water 11 

Absorptive Poioer of Gases. 



Air 1 

Oxygen 1 

Nitrogen 1 

Hydrogen 1 

Chlorine 39 

Carbonic Oxide 90 



Carbonic Acid. 90 

Nitrous Oxide 355 

Sulphureted Hydrogen .. 390 

Sulphurous Acid 710 

Olefiant Gas 970 

Ammonia 1195 



The last table exhibits the relative absorbing powers 
for heat at 212°. The absorbing power of many vapors 
is quite as remarkable, as is also that of the perfume of 
flowers for rays of obscure heat. Aqueous vapor has 
also a powerful absorbent action on heat of low refran- 
gibility. Among gaseous bodies, the same rule holds 
good as for solids — the best absorbents are the best ra- 
diators. 

We see, therefore, that there are different varieties 
of radiant heat. The difference is due to the same 

What is meant by diathermic and athermic bodies? What is the 
absorptive power of ammonia compared with air? What is the 
cause of the varieties of radiant heat ? 

1)2 



82 



RELATIONS OF HEAT AND LIGHT. 



cause which gives different colors to light, namely, that 
heat, being an nnclulatory motion, has waves of various 
lengths, and varying velocity of vibration. In the pris- 
matic spectrum the maximum of heat is found below 
the red end, and it steadily declines on passing toward 
the violet. But in the interference spectrum, produced 
by a ruled grating, as discovered by Prof. J.W. Draper, 
the maxima of heat and light coincide, and are found in 
the centre of the yellow. The prismatic spectrum in- 
duces the supposition that heat is produced by slower 
and longer vibrations than those of light, but the inter- 
ference spectrum corrects this hypothesis, and shows 
that they coexist in the same place at the same time, 
and are probably one and the same force. Obscure heat 
is invisible light, and light, when extinguished, pro- 
duces heat. 

The apparatus by the aid of which Melloni prosecu- 
ted his extensive researches on heat is shown in Fig. 63. 



Fig. 63. 




At M is a stand for the source of heat, with a concave 
mirror for concentrating the rays ; at N, a perforated 
screen ; at P, a plate of the substance to be examined ; 
at T, a thermo-electric pile ; at G, a galvanometer. S 
is an unperforated screen that can be turned down, out 
of the way. 

What is the distribution of heat in the prismatic spectrum ? 
What is the distribution in the interference spectrum ? What is the 
relation between light and heat ? 



THEOEY OF EXCHANGES OF HEAT. 



LECTURE XVI. 

Theory of the Exchanges of Heat.— delations of 
Light and Heat. — Theory of Exchanges. — Explana- 
tion of the Cold Ray Experiment. — Wells's Theory 
of the Dew. — Cold on Mountain Tops. — Tempera- 
ture of the Sun. — Polarized Seat. — Heat of Chemi- 
cal Combination. 

The facts which militate against the doctrine of the 
unity of light and heat are, 1st, that the relations of 
transparency for the two are not the same, smoky 
quartz or dark-colored mica allowing heat, but not light, 
to pass ; and, 2d, that the radiations from such a source 
as a vessel of hot water are not visible to the eye, and 
can not be made to assume the luminous condition. 
But it has been shown by Tyndall that if the heat com- 
ing from an electric lamp, which has passed through an 
opaque solution of iodine in bisulphide of carbon, be 
concentrated upon a thin strip of platinum, it will cause 
the strip to .gjlow, though the eye, when screened by the 
solution, ma^be directed to the sun without perceiving 
the faintest trace of light. In that case heat has been 
converted into light. Such phenomena are included 
under the term Calorescence. , 



Theory of the Exchanges of Heat. 

The theory of the exchanges of heat, comprehending 
an explanation of a great many of the phenomena we 
ordinarily witness, depends on the following principles. 
It assumes, 1st, that all bodies, no matter what their 
temperature may be, are constantly radiating heat at 
all times ; 2d, that the ratio of radiation depends on the 
temperature, increasing as the temperature rises, and 
diminishing as it declines. 

Thus the various objects around us are constantly 
emitting heat, the warm bodies to the cold, and the 
cold ones to the warm. A mass of snow and a red-hot 

\yhat facts militate against the unity of light and heat? De- 
scribe Tyndall's experiment. What is" Calorescence ? On wlnft 
does the theory of the exchanges of heat depend? 



84 THEOEY OF EXCHANGES OF HEAT. 

cannon-ball respectively give off heat, the ball emitting 
it in greater quantities and the snow in less. And, even 
when the adjacent bodies have reached the same ther- 
mometric point, they still continue to exchange heat 
with one another. 

Upon these principles we can readily account for the 
fact that bodies of different temperatures at first, finally 
come to an equilibrium. If an ignited cannon-shot be 
placed in the middle of a large room, it radiates heat to 
the ceiling, the walls, the floor, and the various objects 
around; they also radiate back upon it. But, from its 
elevated temperature, it emits its heat faster than they, 
and therefore gives out more than it receives. Its tem- 
perature constantly descends, and continues to do so 
until it receives just as much as it gives, which takes 
place when it has reached the same degree as the ob- 
jects around; for, other things being equal, bodies at 
the same temperature radiate with equal speed. 

The process must, however, stop as soon as that 
equality of temperature is attained ; for, if we suppose 
the shot to cool below that point, it would evidently 
begin to receive more heat from the objects around 
than it gave forth ; and the excess accumulating in it, 
the temperature would at once rise. 

When an equilibrium is obtained, the process of radia- 
tion still continues, but the exchanges are equal. Two 
lighted candles placed together do not extinguish each 
other or cease to exchange light with each other, nor 
do two bodies equally warm cease for that reason to ex- 
change heat. In a room, therefore, in w^hich every thing 
has the same temperature, rays are continually exchang- 
ing, but each object maintains its own temperature, be- 
cause it receives as much as it gives. 

If a red-hot ball and a thermometer bulb be placed 
near one another, the bulb receives more heat from the 
ball than it gives to it, and its temperature therefore 
rises ; but if a thermometer bulb and a snowball be 
placed in presence of one another, the bulb, being the 
hotter body, gives more than it receives, and its temper- 
How do bodies of different temperatures come to an equilibrium ? 
When does the descent of temperature cease? What is the reason 
thfit it ceases ? Does radiation continue when an equilibrium is 
reached? Give the explanation of the cold ray experiment. 



85 

ature therefore descends. This is the explanation of 
the cold ray experiment with the conjugate mirrors. 
That experiment, as was observed, affords no proof that 
there are rays of cold ; the effect is due to the fact that 
a mutual exchange is going forward between the two 
bodies, and the temperature of the hotter descends. The 
mirrors of course take no part in this phenomenon ; their 
office is merely to direct the path of the rays, as has been 
explained. 

On the principles of the radiation of heat is founded 
Wells's theory of the dew* After the sun goes down 
of an evening drops of water condense on the leaves, 
grass, stones, and other objects exposed to the air. It 
was once a question whether this dew descended in the 
form of a light shower, or ascended from the ground. 
There are also certain circumstances, apparently very 
mysterious, attending its formation. The dew rarely 
falls on a cloudy night ; it also apparently possesses a 
selecting power, depositing itself on some bodies in pref- 
erence to others. The theory of Dr. Wells furnishes a 
beautiful explanation of these curious facts. During the 
day the various bodies on the surface of the earth, re- 
ceiving the rays of the sun, become warm, but at night- 
fall, when the sky is unclouded, they begin to cool, for, 
the process of radiation continuing without any source 
of supply, their temperature must descend. While the 
sun shone they received as much heat from him as they 
gave forth to the sky, but, when he is set, the supply is 
cut off, and they therefore cool, and, as there is moisture 
always in the air, their temperature descending, by-and- 
by the dew point is reached, and they become cold enough 
to condense water from the surrounding air. This is the 
dew. And as different bodies, according to the rough- 
ness or physical condition of their surfaces, radiate with 
different degrees of speed, as Leslie's canister proves, 
some of the objects exposed to the sky cool rapidly and 
are covered with dew, but with others the dew point 
is never reached ; hence the apparent selecting power. 
When there is a canopy of clouds over the sky dew can 

^ When does the dew form ? What circumstances attending it seem 
difficult of explanation ? What is Wells's theory of the formation 
of dew ? Why does dew settle on some bodies and not on others ? 
What is the effect of clouds ? 



86 HEAT OF CHEMICAL COMBINATION. 

not form, for the cloud radiates to the earth as much as 
the earth radiates to it — the exchanges are equal, and 
the equilibrium is maintained ; but, if the cloud disap- 
pears, the heat of the surface of the ground escapes away 
into the regions of space. Hence cloudy nights are 
warm, and a clear is often a frosty night. 

For similar reasons mountain tops are always colder 
than valleys. In a valley the radiation is obstructed by 
the sides of the adjacent hills, but on the top of a mount- 
ain the free exposure to the sky permits of unchecked 
radiation. 

An interesting conclusion may be drawn from the con- 
ditions of the passage of radiant heat through glass. 
We have seen it is necessary that the heat should come 
from a source of very high temperature to pass this me- 
dium with facility. Now the heat of the sun passes it 
with the greatest freedom, as is shown when we stand 
before a window through which the sun shines* In the 
focus of a convex lens bodies may be readily set on fire. 
We infer, therefore, that the temperature of the sun is 
very high, a result corroborated by proofs from other 
sources. 

Radiant heat is susceptible of polarization by tourma- 
lines, and transmission through bundles of mica set at a 
proper angle to the incident ray. It also exhibits the 
phenomena of diffraction and interference. 

The quantity of heat produced by chemical combina- 
tion is definite, though the precise determination of its 
amount is difficult, owing to the complication w r ith latent 
heat and changes of volume. By the aid of delicate cal- 
orimeters, tables of the heat evolved during combustion 
and combination have been constructed, and it has been 
proved that, for example, the union of a given amount 
of oxygen with the various elements does not in all cases 
produce the same quantity of heat. Substances present- 
ing different allotropic conditions evolve in combustion 
different quantities of heat. In many decompositions 
a large development of heat is seen, as when chloride 
of nitrogen or gun cotton is exploded. In precipitations, 

Why is a mountain top colder than a valley? What reason is 
there for supposing the temperature of the sun to be high ? How 
may radiant heat be polarized ? Is the amount of heat produced in 
chemical combination definite? 



PRODUCTION OF LIGHT. 87 

as well as in the reaction of acids upon bases, and solu- 
tion of salts and gases, disturbances of temperature oc- 
cur. It is stated that, during the combination of equiv- 
alent quantities of the different acids with a given base, 
nearly the same amount of heat is produced. But these 
inquiries are as yet very incomplete. 

The great source, however, of all the heat, and indeed 
all the force exhibited in the various manifestations on 
the face of the globe, is the sun ; that from other sources 
is but insignificant in comparison. He is the prime 
mover, and his extinction would make the earth a deso- 
late waste like the visible side of the moon. 



LECTURE XVII. 

Of Light.— Sources of Light.— The Sun.— Incandes- 
cence. — Combustion. — Colors of Lights.— Shadows. 
— Conditions of the Intensity of Light.— Photome- 
ters : Rumford's, Ritchie's, Extinction of Shadows, 
Chlorine and Hydrogen.— Velocity of Light.— Re- 
fection and Refraction. — Bur niiig -glasses. 
Light may be artificially produced by many different 
processes, such as the ignition of solids, combustion, and 
phosphorescence. Any solid, if sufficiently heated, be- 
comes luminous, combustible gases take fire at a certain 
temperature in the air, and the diamond will emit a phos- 
phorescent glow in a dark place after it has been exposed 
to the day. It is, however, as has just been remarked 
in the case of heat, to the sun that we are chiefly indebt- 
ed. The quantity of light furnished by him far exceeds 
that of all natural or artificial sources, and its brilliancy 
is so great that the electric spark alone rivals it. 

When the temperature of solid substances is raised to 
1000° they begin to be luminous in the daylight, or, as 
it is termed, are visibly red-hot. It requires a far high- 
er temperature to render a gas incandescent. This may 
be shown by holding a piece of thin platinum wire in 
the current of hot air which rises from the apex of the 

What is the principal source of heat? How may light be pro- 
duced artificially? What is the point of incandescence of solids* 
J low may we puove that that of gases is higher? 




88 ARTIFICIAL LIGHT. 

flame of a lamp. The air is not visibly ignited, but the 
platinum wire instantly becomes red-hot, showing a great 
difference in this respect between this metal and a gas. 
Different vapors and gases evolve different quantities 
of light when ignited. The flame of burning hydrogen 
is scarcely visible in the daylight ; that of alcohol is but 
Fi 64 little brighter, but, under the same 

circumstances, sulphuric ether emits 
' much light. If we take a glass of 
the form Fig. 64,' consisting of a 
bulb, a j and a curved tube, 6, and, 
having filled the bulb with ether, 
cause it to boil by the application 
of a lamp, c, the ether may be set 
on fire as it is forced out of the vessel by the pressure 
of its vapor. It burns in a beautiful arch of great bril- 
liancy ; but if w^e substitute alcohol for ether the light 
becomes quite insignificant. 

The light which is emitted by lamps and candles is, 
however, in reality due to the disengagement of solid 
matter. The constituents of the gas which produce the 
flame are carbon and hydrogen chiefly ; of these the lat- 
ter is the more combustible, and is first burned ; for a 
moment the carbon exists in a solid form in a state of 
extreme subdivision, and at a high temperature, but, be- 
ing in contact with the external air, it is immediately 
consumed. 

Artificial lights differ in color. If alcohol be mixed 
with common salt and set on fire, the flame is of a yel- 
low tint ; if with boracic acid, it is green ; if with ni- 
trate of strontian, it is red. It is upon these principles 
that the art of pyrotechny depends. 

From whatever source light may come, it exhibits the 
same physical properties. It moves in straight lines. 
When it impinges on polished metallic surfaces it is re- 
flected, on dark surfaces it is absorbed, on transparent 
surfaces, as glass, it is transmitted. In the last case it 
is frequently forced into a new path, as we shall pres- 
ently see, and then the phenomenon takes the name of 

Do all substances evolve the same amount of light in burning? 
What renders the flame of a candle luminous ? How may flames 
be colored ? Mention some of the properties of light. What is re- 
fraction ? 



SHADOWS. 89 

refraction, because the ray is broken from its primitive 
course. 

There are two different kinds of opacity, black and 
white. Charcoal is a black opaque substance, earthen- 
ware is opaque white. 

The shadows formed by opaque bodies arise from the 
interception of light in its rectilinear progress. They 
may be of two different kinds, the common and the ge- 
ometrical. The former arises from a luminous surface, 
the latter from a lucid point. The former consists of 
two portions, the umbra and penumbra / in the latter 
case the passage from total darkness to light on the side 
of the shadow is abrupt, and without the intervention 
of any shade. 

The illuminating power of a light depends upon sev- 
eral conditions. As the distance increases it becomes 
less, the effect being inversely as the square of the dis- 
tance ; that is, at two feet it gives only one fourth of 
*what it would do at one; at three feet, only one ninth. 
The absolute intensity of the light also determines the 
result ; thus, there are flames that are very brilliant, and 
others that are paler. The magnitude of the luminous 
surface is another of these conditions ; the absorbent 
effect exerted on the passing rays by the air, or medium 
traversed, another ; as is also the direct or oblique man- 
ner in which the rays are received on the illuminated 
surface. 

Of Photometers and the Measurement of Light. 

The methods resorted to for the measurement of light 
are quite numerous, the most common being Rumford's 
method, Ritchie's method, the method of the extinction 
of shadows, and the chlorine-hydrogen photometer. 
The precipitation of gold from its chloride by the aid 
of peroxalate of iron, a process invented by Dr. J. C. 
Draper, and various photographic operations, are more 
or less used for special purposes. 

Rumford's depends on the principle that, of two 
lights, the most brilliant will cast the deepest shadow. 

What is the cause of shadows ? What is the difference between 
common and geometrical shadows? What does the illuminating 
power of a light depend upon ? What are the principal methods of 
photometry? Describe Rumford's method. 



90 



PHOTOMETRY. 



If, therefore, the lights- to be compared are made to 
cast shadows of the same opaque body side by side on 
a piece of paper, the eye can without difficulty determ- 
ine which of the shadows is darkest, and the light 
which casts it, being moved to a greater distance, or 
the other brought nearer, when the two shadows are 
of precisely the same depth, the distances of the lights 
from the paper will indicate their relative illuminating 
power. Thus, if one is tw T ice as far off as the other, its 
intensity is four times as great. 

Ritchie's photometer depends on the equal illumina- 
tion of surfaces. It 
consists of a box, 
a 5, six or eight 
inches long, and 
one broad and 
deep, Fig. 65, in 
the middle of 
which a wedge of 
wood, f e g, is 
placed, with its an- 
gle, 6, upward. 
This wedge is cov- 
ered with white paper neatly doubled to a sharp line at 
e. In the top of the box there is a conical tube, with 
an aperture, d, at its upper end, to which the eye is ap- 
plied, and the whole may be raised to any suitable 
height by means of the stand c. On looking down 
through c?, having previously placed two lights, m n, 
the intensity of which we desire to determine, on oppo- 
site sides of the box, they illuminate the paper sur- 
faces exposed to them, and the eye sees both those sur- 
faces at once. By changing the position of the lights, 
we eventually make them illuminate the surfaces equal- 
ly, and then, measuring their distances from e, their il- 
luminating powers are as the squares of those distances. 
In both this and the preceding method a difficulty 
arises when the lights to be compared are of different 
tints. To some extent this may be avoided in Ritchie's 
instrument by placing a colored glass at d. 

The method of extinction of shadows is much more 

Describe Eitchie's photometer. How is it used ? What difficulty 
is there with these two methods ? 




PHOTOMETERS. 



91 



Fig. 6G. 



exact, differences in the colors of the lights even serv- 
ing to give greater accuracy. It depends on the follow- 
ing principle. If a light is made to throw the shadow 
of an opaque object upon a white screen, there is a cer- 
tain distance at which, if a second light be brought, its 
rays illuminating the screen, will totally obliterate all 
traces of the shadow. It has been found that eyes of 
average sensitiveness fail to distinguish the effect of a 
light when it is in presence of another sixty-four times 
as intense. The precise number varies with different 
eyes, but to the same eye it is always the same. If 
there be any doubt as to the perfect disappearance of 
the shadow, the receiving screen may be agitated or 
moved a little : this brings the shadow, to a certain ex- 
tent, into view again. Its place can then be traced, and, 
on ceasing the motion, the disappearance verified. 

When, therefore, we desire to ascertain the relative 
intensities of lights, we have only to determine at what\ 
distance they will extinguish a given 
shadow. Their intensities are as 
the squares of those distances. 

The chlorine-hydrogen photom- 
eter, invented by Professor J. W. 
Draper, depends on the fact that 
chlorine and hydrogen, if mixed in 
the proper proportion to form hy- 
drochloric acid, do not unite in the 
dark, but, if exposed to even a fee- 
ble light, combine, the gases con- 
tracting more quickly as the light 
is stronger, and turning into the 
acid. The contrivance consists of 
a glass tube, a b c d, Fig. 66, with 
three^ platinum wares, fg /i, fused 
into it. From one end, c?, a fine 
tube, e, projects, provided with a 
scale; the other end, a, is closed. 
The stand h supports the whole. 
When the instrument is to be used, 
it is filled with hydrochloric acid, 
and the wires / and g connected with a voltaic bat- 

What is the principle of the method of extinction ? Describe the 
chlorine-hydrogen photometer. How is it made ready for use ? 




92 



BURNING-GLASSES. 



/ 



tery, so that chlorine may be evolved from g and hydro- 
gen from f. As soon as the acid in the limb a b h is 
saturated with chlorine, the pole of the voltaic battery 
that had been connected with f is dipped into the mer- 
cury cup of h. Chlorine and hydrogen then accumulate 
together at a 5, which part is to be covered with an 
opaque screen. The acid at the same time rises in the 
fine tube e. 

On taking off the screen over a b and exposing the 
photometer to light, the chlorine and hydrogen at once 
commence to unite, and the acid descends in the tube e. 
The amount of action can be quantitatively ascertained 
by examining the scale. If exposed to sunlight, a vio- 
lent explosion will result, and the instrument be destroy- 
ed. This photometer was extensively used by Professor 
Draper in his Researches on Light, published in the 
Philosophical Magazine. 

Light does not move from point to point instanta- 
neously, but at a rate which is measurable. From ob- 
servations on the eclipses of Jupiter's satellites, and the 
experiments of Foucault and Fizeau, it appears that this 
velocity is about 192,000 miles per second. 

When a ray falls upon a polished surface it suffers 
• Fig. 6T. reflection, and when it falls 

on a transparent medium 
it undergoes refraction. It 
is in consequence of this 
that convex lenses, as in 
Fig. 67, converge the rays 
of the sun, and so produce 
a high temperature. In 
this application they are 
called burning-glasses, and, 
until the invention of the 
voltaic pile and oxyhydro- 
gen blowpipe, presented 
the most energetic means for elevation of temperature. 
If made of a diameter from one to three feet, they will 
effect the fusion of most earthy and metallic bodies. 
Even gold and silver volatilize at the focus. 

How is the amount of light known ? What is the velocity of light ? 
What are burning-glasses? How high a temperature will they pro- 
duce? 




THE SOLAR SPECTRUM. 93 



LECTURE XVIII. 

The Constitution of Solar Light. — Newtorfs Dis- 
coveries. — The Solar Spectrum. — Order of Intensity 
of Light. — Fluorescence. — Chemical Effects of Light. 
— Fraunhofer } s Lines. — Spectral Analysis. — Chem- 
ical Composition of the Sun. — The Spectroscope. — 
Photography of the Spectrum. — Electric Spectra. 

Sir Isaac Newton first succeeded in proving the 
compound nature of light by the aid of a glass prism. 
If the shutters of a room be closed, Fig.es. 

and through an aperture in one of 
them a beam of the sun enters, a, 
Fig. 68, it pursues a straight path, 
folio wing the dotted line a e. Now 
let the prism interpose in the posi- 
tion b c, so as to intercept complete- I ^ :: <- ::; 
ly the beam. It goes no longer to e, 
but is bent out of its course and 
moves in the direction d. 

Two striking facts are now to be remarked ; first, the 
ray a is broken or refracted from its path ; and, second, 
instead of forming on the surface d, upon which it falls, 
a w r hite spot, an elongated and beautifully colored im- 
age is produced. These colors are said to be seven in 
number, though they shade imperceptibly into one an- 
other — red, orange, yellow, green, blue, indigo, violet. 
This separation of the colors from one another is desig- 
nated by the term dispersion. 

Newton has shown that white light consists of these 
various colored rays blended together, and their separa- 
tion in the case before us is due to the fact that the 
prism refracts them unequally. On examining the po- 
sition of the colors in relation to the point e, to which 
they would all have gone had not the prism intervened, 
it is ascertained that the red is least disturbed or re- 
fracted from its original path, and the violet most. For 

How may the compound nature of light be proved? What facts 
are remarked on passing light through a prism ? What is disper- 
sion ? What is meant by least and most refrangible rays ? 




94 



THE COLOES OF LIGHT. 




this reason we call the red the least refrangible ray, 
the violet the most refrangible, and the yellow interme- 
diately. 

That the mixture of these colored rays reproduces 
Fi m white light, may be proved by re- 

sorting to any optical contrivance 
which will reassemble them, as, for 
instance, another prism, set with 
its back in the opposite direction 
to the first one, or a color-blender, 
Fig. 69. This consists of a light 
disc mounted upon an axis, around 
which it may be caused to revolve with rapidity. Upon 
Fig. to. ^ ts ^ ace are P am ^ed the seven principal colors. 
On causing it to rotate, the colors blend togeth- 
er and the disc seems nearly white. 

Let v r, Fig. 70, represent the spectrum which 
is given by a sunbeam after its passage through 
a prism, and e the point to which it would have 
gone had not the prism intervened. The order 
of colors, commencing with that which is least 
disturbed from its path or nearest to 6, is as fol- 
lows : 

Red, Blue, 

Orange, Indigo, 

Yellow, Violet. 

Green, 
Besides this difference in color, the light differs in in- 
trinsic brilliancy in the different spaces. Thus, if we 
receive the spectrum on a piece of finely-printed paper, 
we can read the letters in each color at very different 
distances. In the yellow region the light is most bril- 
liant, and there we can read farthest. From this point 
the light declines in brilliancy to the two ends of the 
spectrum, its intensity in the colored spaces being in the 
following order : yellow, green, orange, red, blue, indigo, 
violet. 

It was discovered, however, by Stokes that if the pa- 
per be impregnated with an acid solution of sulphate 

How may the recomposition of white light be effected ? Describe 
the color-blender. What is the order of the colors ? How can we 
show the difference of brilliancy in different parts of the spectrum ? 
What is the order of brilliancy of the colors ? 



RAYS OF CHEMICAL ACTION. . 95 

of quinine, the visibility of the rays at the violet end of 
the spectrum is much increased. He attributed it to 
the lowering of the refrangibility of those extreme rays 
so as to bring them into the visible group. Decoctions 
of horse-chestnut bark shows the phenomenon particu- 
larly well : it is termed fluorescence. 

The alchemists found, centuries ago, that the chloride 
of silver, a substance of snowy whiteness, turns black 
on exposure to light. More recently a great number 
of such bodies have been found — bodies which change 
with greater or less rapidity under the influence of this 
agent. The iodide and bromide of silver, which form 
the basis of photography on glass, are such. In the 
same manner, changes take place in a great variety of 
organic compounds ; the most delicate vegetable hues 
are soon bleached, and, indeed, a ray of light can scarce- 
ly fall on a surface of any kind without leaving traces 
of its action. 

If a piece of paper spread over with chloride of silver 
be placed in the solar spectrum, it soon begins to black- 
en ; but it does not blacken with equal promptitude in 
each of the colored spaces, the effect taking place most 
rapidly among the more refrangible colors, and especial- 
ly in the indigo region. As in the case of heat, the ef- 
fect extends far beyond the limits of the spectrum, and 
where the eye can not discover a trace of light. 

By placing a chlorine-hydrogen photometer success- 
ively in the various colored spaces, we can readily de- 
termine the place of maximum action, and the distribu- 
tion of chemical influence throughout the spectrum. 
The greatest effect is found among the more refrangible 
colors, and from that point diminishes tow r ard each end 
of the spectrum. 

When the aperture which admits a ray of light into 
a dark room, Fig. 68, is a narrow fissure or slit not more 
than one thirtieth of an inch in width, the spectrum 
which is formed by the action of a prism is crossed by 
great numbers of black lines. These, called Fraunho- 
fer's lines, are always found in the same position as re- 

"What is fluorescence? What changes occur in chloride of silver 
in the light ? Mention other substances affected by light. How does 
chloride of silver act in the solar spectrum ? How may the point of 
maximum action be found ? How can Fraunhofer's lines be shown ? 



96 



FRAUNHOFER S LINES. 



spects the colored spaces, and, from the invariability of 
Fig. ti. that position, are used as boundary marks. The 
more prominent ones are designated by the let- 
ters of the alphabet, and their relative magni- 
tude and position is given in Fig. 71. 

When, instead of solar light, light from other 
sources, as a candle, the stars, the electric spark, 
etc., is used, the number and position of the 
lines is entirely changed. On causing various 
bodies to volatilize in the flame of a spirit-lamp 
or gas-burner, a characteristic bright group ap- 
pears for each, and by the aid of a prism prop- 
erly arranged, we are enabled to find out the 
chemical composition of many bodies, and even 
ascertain the presence of traces too minute to 
be detected in any other manner. This branch 
of chemical inquiry, called spectroscope analysis, 
received a great impulse from the discovery, by Kirch- 
hoffand Bunsen, of two new metals, caesium and rubid- 
ium, in certain mineral waters. The former gives char- 
acteristic blue lines in the spectrum, the latter red ones. 
They also made the discovery that on passing a beam 
of light from an ignited solid, which was shown by 
Professor Draper to have no fixed lines, through a flame 
in which such a substance as sodium, for example, was 
volatilizing, instead of the bright yellow lines usually 
given by that substance appearing, there came, in their 
place, black lines, the flame having absorbed the rays it 
would otherwise have yielded. They w T ere hence led to 
conclude that the lines in the solar spectrum are due to 
the absorptive action of the atmosphere of that body, 
and that we could infer his chemical composition by com- 
paring the solar spectrum with that of flames in which 
the various elements were burning. In the same man- 
I ner the composition of the stars has been examined. 
The atmosphere of the sun contains sodium, potassium, 
magnesium, calcium, iron, chromium, and nickel, besides 
many other substances. The only difficulty in the way 
of this hypothesis is, that it is known that a change in 
temperature may vary the position of the spectral lines. 

How are they designated ? Are they the same in all kinds of 
light? What is spectroscope analysis? What were Bunsen and 
Kirchhoff's discoveries? What metals are found in the sun? 



THE SPECTROSCOPE. 



97 



The instrument, the spectroscope, which is in common 
use in laboratories, is constructed as follows : P, Fig. 72, 



Fig. 72. 




represents a flint glass prism, supported on a firm 
stand, F. The tube A has a lens at the end next the 
prism, and a vertical slit at the other, the tube being of 
such a length that the focus for parallel rays falls on the 
slit. At JB is an observing telescope, having a lens at 
the end next the prism, and an ey apiece at the other : 
it is adjustable by the two screws a b. The telescope C 
has also a lens toward the prism ; but at its other end, 
and in the focus of the lens, is a scale on an opaque 
ground, which is to be illuminated by a feeble light ; 
d is an adjusting screw. 

In the use of the instrument, the substance to be ex- 
amined is placed in the flame, 6, of a gas burner, F. The 
rays pass down the tube A, are rendered parallel by its 
lens, pass through the prism, are refracted and suffer 
dispersion, and the resulting spectrum is examined by 
the telescope B. As a reflection of the scale C is seen 
at the same time in the field of J5, the position of the 
different lines may be measured. By the aid of the 
flame Z> and a reflector, two spectra may be seen in JB 
at the same time. 

Describe the construction of the spectroscope. How is it used? 

E 



98 



FIXED LINES OF THE SPECTRUM. 



The delicacy of the reactions is shown by the state- 
ment, that by the aid of the spectroscope 260 S 0off of a 
grain of sodium can be detected. 

The position of many of these fixed lines of the solar* 
spectrum, including those at the more refrangible end, 
has been determined by the aid of photography, Pro- 
fessor Draper having first photographed them in 1842, 
and discovered four great groups, containing many hund- 
red lines, which he named M, N, O, P, and which are in- 
visible to the eye. 

Fig. 73. 




What is the delicacy of spectral reactions? 
tography in spectral analysis? 



Of what use is pho- 



SPECTRA OF VARIOUS BODIES. 



99 



The spectra of many substances can only be seen by 
having recourse to the aid of RuhmkorfPs coil, the term- 
inal wires being coated with the body to be tried, or 
else the spark passed through a vessel or tube co'ntain- 
ing it. 

In Fig. 73, No. 1 shows the principal dark lines of the 
solar spectrum ; 2 represents the spectral lines or bands 
produced by the absorbing action of bromine ; 3, those 



C J? a A 




What does Fig. 78 represent ? 



100 THE ETHEK. 

of nitrous acid ; 4, those of perchloride of manganese ; 
5 is the spectrum obtained by burning chloride of cop- 
per in alcohol ; and 6, boracic acid in alcohol. 

In Fig. 74 the solar spectrum, with its principal lines, 
is placed above, and below, in order, are the spectra of 
potassium, sodium, lithium, rubidium, caesium, stron- 
tium, calcium, barium, and thallium. 



LECTURE XIX. 

Wave Theory of Light. — Proofs of the Existence of 
the Ether. — Light consists of Waves in it. — The 
Ethereal Particles move but little. — distinction be- 
tween 'Vibration and Undulation. — FresneVs Theory 
of Transverse Vibrations. — Transverse and Normal 
Waves. — Brilliancy of Light depends on AmjMtude 
of Vibration. 

The cause of light is an undulatory movement taking 
place in the ethereal medium. That such a medium ex- 
ists throughout all space, seenis to be proved by a num- 
ber of astronomical facts. It exerts a resisting agency 
on bodies moving in it. From its tenuity, we should 
scarcely expect that it would impress a marked disturb- 
ance on the great planetary masses, but on cometary 
bodies that are light and gaseous it produces a percept- 
ible action. The comet of Encke, with a period of about 
1200 days, is accelerated in each revolution by about two 
days, and that of Biela, with- a period of 2460 days, is ac- 
celerated by about one day. As there is no other obvi* 
ous cause for these results, astronomers have very gen- 
erally looked upon them as corroborative proofs of the 
existence of a resisting medium — that universal ether to 
which so many other facts point. 

In this elastic medium undulatory movements can be 
propagated in the same manner as waves of sound in 
the air. It is to be clearly understood that the ether 
and light are distinct things ; the latter is merely the 
effect of movements in the former. Atmospheric air is 
one thing, and the sound which traverses it another. 

What does Fig. 74 represent ? What is the cause of light ? What 
proofs have we of the existence of an ether ? What distinction is to 
be made between ether and light ? 



NATURE OF UNDULATIONS. 101 

The air is not made up of the notes of the gamut, nor is 
the ether composed of the seven colors of light. 

Across the ether undulatory movements, resembling 
in many respects the waves of sound in the atmosphere, 
traverse with prodigious velocity. From the eclipses 
of Jupiter's satellites and other astronomical phenom- 
ena, it appears that the rate of the propagation of light, 
or the velocity with which these waves advance, is about 
192,000 miles in a second. We are not, however, to un- 
derstand by this that the ethereal particles rush forward 
in a rectilinear course at that rate : those particles, far 
from advancing, remain stationary. 

If we take a long cord, Fig. 75, and, having fastened 
it by the extremity, 5, to a fixed obstacle, commence 
agitating the end a up p ig% T5> 

and down, the cord | 

will be thrown into a ^^ ^^ _^ ^=^ \ 
wavelike motions pass- 
ing rapidly from one 
end to the other. This may afford us a rude idea of the 
nature of ethereal movements. The particles of which 
the cord is composed do not advance or retreat, though 
the undulations are rapidly passing. 

A distinction is to be made between the words vibra- 
tion and undulation. In the case of the cord, Fig. 75, 
the vibration is represented by the movement exerted 
by the hand at the free extremity, a ; the undulation is 
the wave-like motion that passes along the cord. We 
see, therefore, that these stand in the relation of cause 
and effect : the vibration is the cause, and the undula- 
tion the effect. Throughout the ethereal medium, each 
particle vibrates, and transmits the undulatory effect to 
the particles next beyond it. 

In the same way as a vibrating cord agitates the sur- 
rounding air and makes waves of sound pass through 
it, so does an incandescent or shining particle, vibrating 
with prodigious rapidity, impress a wave-like motion on 
the ether, and the movement eventually impinging on 
the eye is what we call light. 

To refer again to the simple illustration given in 

What is the velocity of light ? What does Fig. 75 illustrate ? 
What is the distinction between vibration and undulation? How 
does a shining particle communicate an impression to the eye ? 



102 THEORY OF TRANSVERSE VIBRATIONS. 

Fig. 75, it is obvious that there is an infinite variety 
of directions in which we may vibrate that cord, or 
throw it into undulations. We may move it up and 
down, or horizontally right and left, and also in an infi- 
nite number of intermediate directions, every one of 
Fig. 76. which is transverse, 

, f? or at right angles to 

(a the length of the 

c \/\f-^ x — '""^ — -^""^ — ^ cord, as a a, 5 5, cc, 
\j)fe etc., Fig. 76. This is 

a the peculiarity of the 

movement of light. Its vibrations are transverse to the 
course of the ray, and in this it differs from the move- 
ment of sound, in which the vibrations are normal; that 
is to say, in the direction of the resulting wave, and not 
at right angles to it. 

This great discovery of the transverse vibrations of 
light was made by M. Fresnel. 

It may, however, be remarked, that though light con- 
sists of rays originating in these transverse motions, it 
is not impossible that there may be other phenomena 
which correspond to movements in other directions. 
To those movements our eyes are totally blind, and 
hence we can not speak of them as light. In the same 
way there may be motions in the air due to transverse 
vibrations, but to them our ear is perfectly deaf. 

Lights differ from each other in two striking particu- 
lars — brilliancy and color. These are determined by 
certain qualities in the waves. On the surface of water 
we may have a wave not an inch in altitude, or a wave, 
as the phrase is, " mountains high." Under these cir- 
cumstances waves are said to differ in amplitude ; and 
transferring this illustration to the case of light, a wave, 
the amplitude of which is great, impresses us with a 
sense of intensity or brilliancy ; but a wave, the ampli- 
tude of which is less, is less bright. The brilliancy of 
light depends on the magnitude of the excursions of the 
vibrating particles. 

In how many ways may a cord be vibrated ? Are other motions 
of the ether possible? In what particulars do lights differ? What 
is the cause of the difference in brilliancy ? 



COLORS DEPEND OX WAVE LENGTPI, 



103 



Fig. TT. 



L 



\J 



LECTURE XX. 

Wave Theory of Light. — Colors of Light depend 
upon Wave Lengths. — Interference of Sounds. — 
Young *s Theory of the Interference of Light. — Con- 
ditions of Interference. — Explanation of Lights and 
Shades in Shadows. 

By the length of a wave upon water, we mean the dis- 
tance that intervenes from 
the crest of one wave to that 
of the next, or from depres- ' 
sion to depression. Thus, in 
Fig. 77, from a to c consti- 
tutes the wave length, and from a to b its altitude or 
height. 

In the ether the length of waves determines the phe- 
nomenon of color. This may be rigorously proved, as 
we shall soon see when we come to the methods by 
which philosophers have determined the absolute lengths 
of undulations. It has been found that the longer waves 
give rise to red light, the shorter ones to violet, and 
those of intermediate magnitudes, the other colors in 
the ord^r of their refrangibility. 

Two rays of light, no matter how brilliant they are 
separately, may be brought under such relations to one 
another as to destroy each other's effect and produce 
darkness ; two sounds may bear such a relation to each 
other that they shall produce silence ; and two waves on 
the surface of water may so interfere with one another 
that the water shall retain its horizontal position. 

Take two tuning-forks of the same note, 
and fasten by a little sealing-wax on one 
prong of each a disc of cardboard half an 
inch in diameter, as seen in Fig. 78, a. Make 
one of the forks a little heavier than the oth- 
er by putting on the end of it a drop of the 
wax. 

Then take a glass jar, 5, about two inches 
in diameter and eight or ten long, and hav- 

What is meant by wave length ? What effect has the length of 
undulation on the color of light ? Describe the experiment Fig. 78 




104 TWO SOUNDS PRODUCE SILENCE. 

ing made one of the forks vibrate, hold it over the 
mouth of the jar, as seen at c?, its piece of cardboard be- 
ing downward ; commence pouring water into the jar, 
and the sound will be greatly re-enforced. It is the col- 
umn of air in the jar vibrating in unison with the fork, 
and we adjust its length by pouring in the water. 
When the sound is loudest we cease to pour in any 
more water, the jar is adjusted, and we can now prove 
that two sounds added together may produce silence. 

It matters not which fork is taken, whether it be the 
light or the loaded, on making it vibrate and holding it 
over the mouth of the resonant jar, we hear a uniform 
and clear sound, without any pause, stop, or cessation. 
But if we make both vibrate over the jar together, a re- 
markable phenomenon arises — a series of sounds alter- 
nating with a series of silences; for a moment the sound 
increases, then dies away and ceases, then swells forth 
again, and again declines ; and so it continues until the 
forks cease vibrating. The length of these pauses may 
be varied by putting more or less wax on the loaded 
fork ; and as we can see that, even during the periods 
of silence, both forks are rapidly vibrating, the experi- 
ment proves that two sounds taken together may pro- 
duce silence. 

Under these circumstances, waves of sound are said 
to interfere with each other, and in like manner inter- 
ference takes place among the waves of light. We can 
gather an idea of the mechanism by considering this 
case in weaves upon water, in w T hich, if two undulations 
encounter each other under such circumstances that the 
concavity of the one corresponds with the convexity of 
the other, they mutually destroy each other's effect. 

If two systems of waves of the same length encoun- 
ter each other after having come through paths of equal 
length, they will not interfere; nor will they interfere, 
even though there be a difference in the length of these 
paths, provided that the difference be equal to one whole 
wave, or two, or three, etc. 

But if two systems of waves of equal length encoun- 

What is the use of the jar of water? How may silence be pro- 
duced by the vibrating tuning-forks? What is meant by interfer- 
ence of sound ? How may it be illustrated by waves on water ? Un- 
der what circumstances do undulations re-enforce one another ? 



LAWS OF INTERFERENCE. 



105 




ter each other after having come through paths of un- 
equal length, they will interfere ; and that interference 
will be complete when the difference of the paths through 
which they have come is half a wave, or 1^-, 2 J, 3^, etc. 

These cases are respectively shown at a b and c d. 
Fig. 7 9, at the point of encounter, x. Fig. 79. 

In the first instance, the two sets of 
waves are in the same phase, that is, 
their concavities and convexities re- 
spectively correspond, and there is 
no interference ; but in the second 
case, at the point of encounter, cc, the 
two systems are in opposite phases, 
the convexity of the one corresponding with the con- 
cavity of the other, and interference takes place. 

Upon these principles we can account for the remark- 
able results of the following experiment : From a lucid 
point, 5, Fig. 80, which may be Fig.80. 

formed by the rays of the sun con- 
verged by a double convex lens of 
short focus, or by passing a sun- 
beam through a pinhole, let rays 
emanate, and in them place an 
opaque -obstacle, a 5, which we will 
suppose to be a cylindrical body, 
seen endwise in the figure. At 
some distance beyond place a screen of white paper, 
c d, to receive the shadow. It might be supposed that 
this shadow should be of a magnitude included Fig. 8i, 
between x y, because the rays s a, s 5, which pass 
the sides of the obstacle, impinge on the paper at 
those points. It might farther be supposed that 
within the space x y the shadow should be uni- 
formly dusky or dark, but on examining it such 
will not be found to be the case. The shadow 
will be found to consist of a series of light and 
dark stripes, as represented in Fig. 81. In its 
middle, at e, Figs. 80 and 81, there is a white stripe; 
this is succeeded on each side by a dark one, this again 
by a bright one, and so on alternately. 

Under what circumstances do they interfere ? Describe Fig. 79. 
Describe the experiment Fig. 80. What is seen on the screen ? 
How is this explained on the undulatory theory ? 

E2 




106 IXTERFEKENCE OF LIGHT. 

Upon the modulatory theory all this is readily ex- 
plained. Sounds easily double round a corner, and are 
heard though an obstacle intervene. Waves upon wa- 
ter pass round to the back of an object on which they 
impinge, and the undulations of light in the same man- 
ner flow round at the back o'f the cylinder a 5, Fig. 80. 
And now it is plain that two series of waves which have 
passed from the sides of the obstacle to the middle of 
the shadow, that is, along the lines a e, b 6, have gone 
through paths of equal length, and, therefore, when they 
encounter at the point e, they will not interfere, but ex- 
alt each other's effect. 

But, leaving this central point, e, and passing to /*, it 
is plain that the systems of w r aves which have come' 
through the paths af, bf, have come through different 
distances, for bfis longer than af; and if this differ- 
ence be equal to the length of half a wave, they will, 
when they encounter at the point f, interfere and de- 
stroy each other, and a dark stripe results. 

Beyond this, at the point g, the waves from each side 
of the obstacle a g, b g, again have come through un- 
equal paths ; but, if the difference is equal to the length 
of one whole wave, they will not interfere, and a w r hite 
stripe results. 

Reasoning in this manner, we can see that the inte- 
rior of such a shadow consists of illuminated and dark 
spaces alternately — illuminated spaces when the light 
has come through paths that are equal, or that differ 
from each other by 1, 2, 3, 4, etc., waves, and dark when 
the difference between them is equal to J, lj, 2 J, 3 J, etc., 
waves. 

That it is the interference of light coming from the 
opposite sides of the opaque object which is the cause 
of these phenomena, is proved by the circumstance that 
if we place an opaque screen on one side of the obsta- 
cle, so as to prevent the light passing, the fringes all 
disappear. 

What is the cause of the white stripe in the centre ? What is the 
cause of the dark stripes on each side, and of the white stripes which 
succeed them ? How can it be proved that these stripes result from 
interference ? 



WAVE LENGTHS. 107 



LECTURE XXI. 

Wave Theory of Light. — Measurement of the Length 
of a Wave of Light, — Lengths differ for different Col- 
ors. — Measurement of the Rapidity of Vibration. — 
Nature of Polarized Light. — Plane, Circular, and El- 
liptical Polarized Light. — Reflection, Refraction, and 
Absorption of Light.— Cause of the Color of Objects. 

The experiment, Fig. 80, may enable us to determine 
the length of a wave of light. This may be done by 
measuring the distances a f and b f or from the sides 
of the obstacle to the first bright stripe from the cen- 
tral one, for at that point the* difference between those 
two lines, afl and b f is equal to the length of one 
wave. We might employ the second bright stripe; 
the difference would then be equal to two waves. 

Farther : if, instead of using ordinary white light, ra- 
diating from the lucid point s, we use colored lights, 
such as red, yellow, blue, etc., in succession, we shall 
find that the wave length determined by the process 
just explained differs in each case ; that it is greatest in 
red, and smallest in violet light. By exact experiments 
made upon methods more complicated than the element- 
ary one here given, it has been found that the different 
colored rays of light have waves of the following length : 

Wave Lengths of the Different Colors of Light. 
The English inch is supposed to be divided into 10 mil- 
lion equal parts, and of those parts the wave lengths are, 



For red light 256 

" orange light 240 

" yellow " 227 

" green " 211 



For blue light 196 

" indigo " 185 

" violet " 174 



In this manner it is proved that the different colors 
of light arise in the ether from its being thrown into 
waves of different lengths. 

Knowing the rate at which light is propagated in a 

How can the length of a wave of light be measured ? What re- 
sults on using various colored lights ? Give the wave lengths of the 
different colors. 



108 



POLARIZATION OF LIGHT. 



second, and the wave length for a particular color, we 
can readily tell the number of vibrations executed in a 
second, for they plainly are obtained by dividing 192,000 
miles, the rate of propagation, by the wave length. 
From this it appears that if a single second of time be 
divided into one million of equal parts, a wave of red m 
light trembles or pulsates 458 millions of times in that 
inconceivably short interval, and a wave of violet light 
727 millions of times. 

Common light, as has been said, originates in vibra- 
tory motions taking place in every direction transverse 
to the ray. With polarized light it is different. To 
gather an idea of the nature of polarized light, we must 
refer once more to the cord, Fig. 76, which, as has been 
said, serves to imitate common light when its extremity 
is vibrated vertically, horizontally, and in all interme- 
diate positions in rapid succession; butrif we simply vi- 
brate it up and down or right and left, then it imitates 
polarized light. Polarized light is therefore caused by 
vibrations transverse to the ray, but which are executed 
in one direction only. 

There is a certain gem, the tourmaline, which serves 
to exhibit the properties of polarized light. If we take 
Fig. 82, a thin plate of this substance, 

c d, properly cut and polished, 
and allow a ray of light, a &, 
Fig. 82, to fall upon it, that 
ray will be freely trarsmitted 
through a second plat 3 if it be 
held symmetrically to the first, as shown at ef; but if 
we turn the second plate a quarter round, as seen at g A, 
then the light can not pass through. The rays of the 
meridian sun can not pass through a 
pair of crossed tourmalines. 

The cause of this is obvious. If we 
take a thin lath or strip of pasteboard, 
c d, Fig. 83, and hold it before a cage 
or grate, a 6, it will readily slip through 
when its plane coincides with the bars; 

How can we determine the number of vibrations of light in a sec- 
ond ? What is the difference between common and polarized light ? 
"What are the properties of the tourmaline ? How are they illus- 
trated by Fig. 83 ? 




Fig. S3. 



IW 



POLARIZED LIGHT. 109 

but if we turn it a quarter way round, as at ef, then, of 
course, it can not pass the bars. Now the plate of 
tourmaline, Fig. 82, c d, polarizes the light, a b, which 
falls upon it ; that is, the waves that pass through it 
are all vibrating in one plane. They pass, therefore, 
readily through a second plate of the same kind so long 
as it is held in such a way that its structure coincides 
with that motion, but if it be turned round so as to 
cross the waves, then they are unable to pass through it. 

There are many ways in which light can be polarized 
— by reflection, refraction, double refraction, etc. The 
resulting motion impressed on the ether is the same in 
all cases. 

Ligfrt modified as just described is designated plane 
polarized light, but there are other varieties of polariza- 
tion. If the end of the rope, Fig. 76, be moved in a cir- 
cle, circular waves will be produced, imitating circularly 
polarized light, and if it be moved in an ellipse, elliptical 
polarized light. 

When a beam of polarized light is transmitted in cer- 
tain directions through plates of double-refracting bod- 
ies, splendid phenomena of coloration are produced. 
Plates of mica, selenite, or quartz, cut in a direction 
parallel' to that of the optic axis, cause the image to as- 
sume a tint which may be made to vary by rotating the 
analyzing plate. If, instead of an analyzing plate in the 
reflecting apparatus, a crystal of calcareous spar be sub- 
stituted, two images are seen, which are tinged of com- 
plementary hues at all parts of the revolution. By 
using a plate cut from an uniaxial crystal perpendicular 
to the optic axis, a series of colored rings, intersected 
by a cross, will be observed. With biaxial crystals, a 
double system of colored rings is formed. In uncrys- 
tallized media, such as glass, which are submitted to 
pressure or not well annealed, the same phenomena are 
shown, and can be varied by altering the shape of the 
piece used. 

The undulatory theory of light gives a clear account 
of the ordinary phenomena of optics. The general law 
under which light is reflected from polished surfaces is 

By what means can light be polarized ? What is circular polar- 
ized light? What is elliptical polarized light? How is coloration 
produced in polarized light ? 



110 LAWS OF REFLECTION AND REFRACTION. 

Fig. 84. a direct consequence of it. That law is, 



f 



h jd that the angle d c b, Fig. 84, made by the 
reflected ray d c, with a perpendicular, c b, 
drawn to the point c, at which the light 
impinges, is equal to the angle a c b, which 
the incident ray makes with the same per- 
pendicular, or, as it is briefly expressed, 
" the angles of incidence and reflection are equal to each 
other, and on opposite sides of the perpendicular." 

By the aid of this law we can show the action of re- 
flecting surfaces of any kind, and discover the proper- 
ties of plane and curved mirrors, whether they be con- 
cave or convex, spherical, elliptical, paraboloidal, or any 
other figure. ^ 

From the undulatory theory, the law of the refraction 
of light also follows as a necessary consequence. It is, 
" In every transparent substance, the sines of the angles 
of incidence and refraction are to each other in a con- 
stant ratio," and by the aid of this law we can determ- 
ine the action of media bounded by surfaces of any 
kind, plane or spherical, concave or convex. It explains 
the action of lenses, and the construction of refracting 
telescopes and microscopes. 

Sir Isaac Newton's discovery that white light arises 
from the mixture of the different colored rays in certain 
proportions explains the cause of the colors which trans- 
parent media often exhibit. Thus, if glass be stained 
with the oxide of cobalt, it allows a blue light to pass 
it ; and upon such principles the art of painting on glass 
depends, different colors being communicated by differ- 
ent metallic oxides. The cause of this effect is readily 
discovered; for, if we make the light which enters a 
dark room, as in Fig. 68, pass through such a piece of 
stained glass before it goes through the prism, and ex- 
amine the resulting spectrum, we find that several rays 
are wanting in it; that the glass has absorbed or de- 
tained some, and allowed others to traverse it. A piece 
of blue thus suffers most of the blue light to pass, but 
stops the green, the yellow, etc. But it is also to be 
observed that the light which is transmitted by^ any of 

What is the law of the reflection of light ? What is the law of 
refraction of light ? What is the cause of the color of transparent 
media ? Is the light transmitted pure ? 



PRODUCTION OF LIGHT. Ill 

these colored media is not pure ; it is contaminated with 
other tints. The blue glass, for instance, does not stop 
all the rays except the blue ; it allows a large portion 
of the red to pass, and hence the light it transmits is 
more or less compound. 

The color of an opaque object is due to the same 
cause, the substance absorbing the rays of one or more 
colors and reflecting the rest. It appears to be of the 
color that it reflects. 



LECTURE XXII. 

Production of Light. — Professor J. W. Draper's Re- 
searches. — By Incandescence. — Point at which Bod- 
ies become Red-hot. — All Solids shine at the same 
Degree. — Colors emitted. — Rate of Increase of In- 
tensity. — Production by Combustion. — Nature of 
Flames. — By Phosphorescence. — Control of Temper- 
ature. — Application of the Theory of Undulations. 

A theoretical explanation of the chemical action of 
light must depend on the views entertained of the na- 
ture of that agent. In a series of memoirs published in 
the London and Edinburg Philosophical Magazine be- 
tween 1847 and 1851, Professor Draper investigated the 
circumstances under which light arises by artificial pro- 
cesses. The chief results obtained are as follows. 

There are three general processes by which light is 
obtained artificially: 1st. By the ignition of bodies; 2d. 
By their combustion or burning ; 3d. By phosphores- 
cence. 

1st. Of the Production of Light by Ignition. — All 
solid substances shine when their temperature is raised 
to a certain degree. The point at which this occurs 
has been variously estimated. Sir Isaac Newton places 
it at 635°, Davy at 812°,Wedgewood at 947°, Daniell 
at 980°. By inventing improved means, Dr. Draper 
found that for platinum it is 977°, or, if Laplace's co- 
efficient of dilatation be used in the calculation, 1006°. 

What is the cause of the color of opaque objects? How may 
light be obtained artificially? What is the temperature to which a 
solid must be raised before it shines ? 



112 



LIGHT BY IGNITION. 



By inclosing a number of different substances with a 
mass of platinum in a gun-barrel, the temperature of 
which was gradually raised, it was found, on looking 
down the barrel, that they all commenced to shine at 
the same moment, and this even though, as in the case 
of lead, the nfelted condition had been assumed. Prof. 
Draper therefore inferred that all solids and liquids be- 
gin to shine at the same degree of the thermometer. 

The color of the light which the ignited substance 
emits depends upon the degree of heat to which it is 
exposed. Making due allowance for the physiological 
imperfections of the eye, there can be no doubt that the 
first rays which appear are the red, and, as the temper- 
ature is made gradually to ascend, the yellow, orange, 
green, blue, indigo, and violet are emitted in succession. 
At 2130° all these colors are exhibited, and from their 
commixture the substance appears white-hot. 

As the temperature of an incandescent body rises, 
therefore, it emits rays of light of increasing refrangi- 
bility. 

By the aid of the method of extinction of shadows, it 
was proved that, as the temperature of an ignited solid 
rises, the intensity of the light increases very rapidly. 
For example, platinum at 2600° emits almost forty 
times as much light as at 1900°, as the following table 
shows. 

Intensity of Light emitted by Platinum at different 
Temperatures. 



Tempeisature of the Platinum. 


Intensity of its Light. 


980° 


0.00 


1900° 


0.34 


2015° 


0.62 


2130° 


1.73 


2245° 


2.92 


2360° 


4.40 


2475° 


7.24 


2590° 


12.34- 



From a parallel series of experiments, in which the 

Do all solids shine at the same temperature? What does the 
color of light emitted by an ignited solid depend upon ? What is 
the first ray that appears? At what temperature are all the colors 
emitted ? What is the relation between the intensity of the light 
and the temperature? 



LIGHT BY COMBUSTION. 113 

heat radiated by the ignited platinum was measured, a 
striking analogy between the two agents appears. Thus, 
if the quantity of heat radiated by platinum at 980° be 
taken as unity, it will have increased at 1440° to 2.5, 
at 1900° to 7.8, at 2360° to 17.8 nearly. The rate of 
increase is, therefore, very rapid, as in the preceding 
case. 

2d. Of the Production of Light by Combustion. — It 
has been long known that all common flames are incan- 
descent shells, the interior of which is dark, and it has 
been supposed that there are certain flames which emit 
particular rays only, but an examination by the prism 
showed that in every flame every prismatic color is 
found. The red which burning cyanogen, and the blue 
which burning sulphur emits, are compound colors. 

By burning solid carbon in oxygen gas, it appeared 
that there is a connection between the refrangibility of 
the light which a burning body yields and the intensity 
of the chemical action going on, and that the refrangi- 
bility always increases as the chemical action increases. 

From this it appears that flames, such as those of 
lamps and candles, consist of a series of concentric and 
differently-colored shells, the most interior one being 
red, and having a temperature of 977°. Upon this, in 
succession, are placed orange, yellow, green, blue, indi- 
go, and violet shells. The flame, looked at directly, ap- 
pears to yield white light because of the commixture of 
these rays ; but, on being submitted to the action of a 
prism, they are separated from each other, and their in- 
dividual existence proved. If, therefore, we could iso- 
late a horizontal section of such a flame, it would have 
the aspect of an iris, or rainbow ring. 

Upon the principle that the more energetic the chem- 
ical action the higher the refrangibility of the light 
emitted, we may explain without difficulty the colors 
which different flames present. The red tints predomi- 
nate in the flame of burning cyanogen, because in that 
gas there is an element wholly incombustible, the nitro- 

What analogy was shown between heat and light ? What is the 
construction of a flame? What relation is there between chemical 
action and refrangibility ? What is the color of the interior of a 
flame ? What colors surround it ? Why is the flame of cyanogen 
red? 



114 COLORS OF FLAMES. 

gen. This, as it is set free, cuts off the free access of 
the air, and the burning goes on tardily, very much in 
the same manner as in an oil-lamp to which the air is 
imperfectly supplied. On the other hand, carbonic ox- 
ide burns blue, because of the small quantity of air re- 
quired to carry it to its maximum of oxidation. The 
color of flames depends, therefore, on the completeness 
or incompleteness of the combustion, this principle read- 
ily accounting for those cases in which means are used 
for retarding or promoting the rate of burning, as where 
an atmosphere of oxygen is used, or air introduced into 
the interior of a flame by means of a blowpipe, the 
bright blue cone arising in this latter instance being a 
striking indication of the increased rapidity of combus- 
tion. 

There is, therefore, a direct connection between the 
vehemence with which chemical affinity is satisfied and 
the refrangibility of the resulting light. If, as there are 
many reasons for supposing, all chemical changes are 
attended by vibratory movements of the particles of the 
bodies engaged, it might well be anticipated that these 
vibrations should increase in frequency as the action be- 
comes more violent ; but it is to be remembered that an 
increased frequency of vibration is the same thing as an 
increased refrangibility. 

3d. Of the Production of Light by Phosphorescence. — 
All solid substances, except the. metals, possess the prop- 
erty of shining after they have been exposed to the sun. 
Even the hand, after being dipped in the sunshine, emits 
subsequently light enough to be .visible in a dark place. 
In some the effect lasts but for a moment, in others it is 
of longer duration and considerable splendor. Among 
the best phosphori may be mentioned the sulphide of 
barium, the sulphide of calcium, certain varieties offluor 
spar and of diamond. Phosphorescence has generally 
been regarded as unattended by the emission of heat. 
It does not require that the exposure to light should be 
protracted ; the flash of an electric spark is sufficient ; 
but the phosphorogenic rays can not pass through glass. 

Why is the flame of carbonic oxide blue ? What does the color 
of a flame depend on ? Why is a blowpipe flame blue ? What sub- 
stances are phosphorescent? Mention some of the best phosphori. 
Is phosphorescence attended by heat ? 



PHOSPHORESCENCE. 115 

By suitable experimental arrangements Professor 
Draper ascertained that the best phosphori, when at 
their maximum of glow, do not increase in volume by 
so much as the i 2 ooo part ; but that there is a minute 
expansion can not be doubted, since, when means suffi- 
ciently delicate are resorted to, a feeble rise of tempera- 
ture can be detected. The intensity of the light disen- 
gaged is to some extent deceptive ; for, by resorting to 
the method of the extinction of shadows, it was shown 
that a fine specimen of chlorophane, at its maximum of 
: brightness, yielded a light three thousand times less in- 
tense than the flame of a very small oil lamp. 

The quantity of light a substance can receive, when 
exposed to the sun, depends on -the temperature. The 
colder the phosphorus is, the more brightly will it sub- 
sequently shine ; if kept hot during its exposure, it will 
not shine at all. If a diamond placed upon ice be sub- 
mitted to the sun and then brought into a dark room 
the temperature of which is 60°, for a time there is a 
glow, but presently the light declines and dies out. Let 
the diamond now be put in water at 100°; again it 
shines, and again its light dies away. If it next be re- 
moved from that water and suffered to cool, and then be 
reimmersed, it will not shine again ; but if the water be 
heated to 200° and the diamond be dropped into it, 
again it glows, and again its light dies away. There 
is therefore a correspondence between the light disen- 
gaged and the temperature applied. 

The phenomena of phosphorescence may all be ex- 
plained on the principles of the theory of undulations ; 
for, from a shining body undulations are propagated in 
the ether, and these, impinging on a phosphorescent sur- 
face, throw its molecules into a vibratory movement. 
These, in their turn, impress on the ether undulations ; 
but, by reason of the difference of its density compared 
with that of the molecules, they do not lose their mo- 
tion at once, but it continues for a time, gradually de- 
clining away, and ceasing when the vis viva of the mol- 
ecules is exhausted. 

We may therefore abandon expressions derived from 

What effect has temperature on phosphorescence ? Describe the 
experiment with a phosphorescent diamond. Explain phosphor- 
escence on the undulatory hypothesis. 



116 CHEMICAL ACTION OF LIGHT. 

the material theory of light, such as absorption and sub- 
sequent emission of the luminous agent, and conclude 
that, whenever a radiation falls upon a surface of any 
kind, it throws the particles thereof into a state of vi- 
bration, as when a stretched string is made to vibrate 
in sympathy with a distant musical sound. This view 
includes at once all the facts of the radiation of heat, on 
the dynamical hypothesis and the theory of calorific ex- 
changes ; it also offers an explanation of the connection 
of the atomic weights of bodies and their specific heats. 
It suggests that all cases of the decomposition of com- 
pound molecules under the influence of light are owing 
to a want of consentaneousness in the vibrations of the 
impinging ray and those of the molecular group, which, 
unable to maintain itself, is broken down, under the pe- 
riodic impulses it is receiving, into other groups, wilich 
can vibrate in unison with the ray. 



LECTURE XXIII. 

Chemical Action of Light. — Action of Natural 
and Artificial Lights. — Preliminary Absorption. — 
Change in the Ray.— Necessity of Absorption. — 
Spectral Impressions. — Light causes Vegetation by 
its Yellow Ray. — Tlie Indigo Ray determines the Di- 
rection of Growth. — Effect of Amplitude, Frequency, 
and Direction of Undulations, 

From whatever source it may be derived, light ex- 
erts chemical action. The moonbeams are sufficiently 
intense to give copies of that satellite on sensitive sur- 
faces, as my father found in 1841. Recently I have suc- 
ceeded, by the aid of a reflecting telescope of 15 \ inches 
aperture which I constructed, in producing photographs 
of that body 50 inches in diameter. Lamplight and 
other artificial lights are often peculiarly energetic. 
These decom]^>sing effects take place on those portions 
of the substance only on which the rays actually fall. 
There is no lateral spreading, nothing analogous to con- 
duction. 

When a sensitive substance receives light for a short 

What is the cause of the decomposition of substances by light ? 
Does the moonlight exert chemical action ? 



CAUSE OF ITS CHEMICAL ACTION. 117 

space of time no change takes place, the rays are being 
actively absorbed ; but as soon as that preliminary ab- 
sorption is over they act in a manner which is perfectly 
definite : if, for instance, it be a decomposition that they 
are bringing about, the amount of decomposing effect 
will be precisely proportional to the quantity of rays 
absorbed. , 

When a beam from any shining source causes a de- 
composing effect, it is always itself disturbed ; the me- 
dium which is changing impresses a change in the ray. 
Thus, a mixture of chlorine and hydrogen unites under 
the influence of a ray, but that portion of the ray which 
passes through the mixture has lost the quality of ever 
bringing about a like change again. 

When a beam from any shining source falls on a 
changeable medium, a portion of it is absorbed for the 
purpose of effecting the change, and the residue is either 
reflected or transmitted, and is perfectly inert as respects 
the medium itself. 

No chemical effect can therefore be produced by rays, 
except they be absorbed. It is for this reason that wa- 
ter is never decomposed by the sunshine, nor oxygen 
and hydrogen made to unite ; for these substances are 
all transparent, and allow the rays to pass without any 
absorption, and absorption is absolutely necessary before 
chemical action can ensue. 

But with chlorine the case is very different. This 
substance exerts a powerful absorbent action on light : 
the effect takes place on the most refrangible rays. 
When mixed with hydrogen and set in the light, it 
unites with a violent explosion. 

As connected with the minute changes of surface 
which are effected when the different radiant principles 
fall upon bodies, as in the case of photography, we may 
allude to the formation of spectral impressions, which, 
though invisible, may be brought out by proper pro- 
cesses. Professor Draper described the following in- 
stance many years ago : Take a piece of polished metal, 
glass, or japanned tin, the temperature of which is low, 

What is meant by preliminary absorption ? What change is im- 
pressed on the ray ? Does the ray undergo absorption ? Why do 
not oxygen and hydrogen unite in the sunshine ? Why do chlorine 
and hydrogen unite ? What are spectral impressions ? 



118 ACTION OF LIGHT. 

and, having laid upon it a wafer, coin, or any other such 
object, breathe upon the surface and allow the breath 
entirely to disappear; then toss the object off the sur- 
face and examine it minutely. 'No trace of any thing 
is visible, yet a spectral impression exists on that sur- 
face, which may be evoked by breathing upon it. A 
form resembling the object at once appears; and what 
is very remarkable, it may be called forth many times 
in succession, and even at the end of many months. 
Other instances of the kind have subsequently been de- 
scribed by M. Moser. 

Light exerts no ordinary control over the phenomena 
of the natural world. Thus it is to its influence that the 
vegetable world owes its existence ; for plants can only 
obtain carbon from the air while the sun is shining on 
them, and it is of that carbon that their solid structures 
are chiefly formed. It has been a question to which ray 
this effect is due, but in 1843 Professor Draper proved 
that it is the yellow light which is involved. Dr. Priest- 
ley discovered that the leaves of plants will effect the 
decomposition of carbonic acid gas under water ; and, 
on immersing tubes filled with water holding this gas 
in solution, and containing a few green leaves, Professor 
Draper found that at the blue extremity of the spectrum 
no effect whatever took place, while decomposition went 
on rapidly in the yellow ray. Dr. Gardner showed, how- 
ever, that the more refrangible rays have the power of 
influencing the direction of growth of plants ; turnip- 
seeds which had germinated in the dark, when placed 
in the solar spectrum, leaning toward the indigo region. 

On the Chemical Action of Light. 

In considering the action of a ray of light upon a de- 
composable body, there are three different points to be 
discussed, so far as the ray itself is concerned: 1st. To 
w T hat extent and in what manner is the result affected 
by the intensity of the ray — that is, by the amplitude 
of the vibrating excursions ; 2d. How is it affected by 
the frequency of the pulsatory impressions ? 3d. How 

What effect has light in the natural world? How did Professor 
Draper show the function of the yellow ray ? What influence has 
the indigo ray on plants? What points have to be considered in 
examining the action «f a ray ? 



PHOTOGRAPHY. 119 

by the direction in which the vibrations are made, as in- 
volved in the idea of polarization ? 

1st. By means of burning lenses Professor Draper 
found that it is not the intensity of a beam which de- 
termines its decomposing power, and that we can not 
produce greater effects by concentrated light, than we 
can by the application of the simple sunbeam continued 
for an equivalent period of time. Nor can such optical 
contrivances effect the decomposition of substances on 
which a feeble beam has no action. 
, 2d. Rays of the highest refrangibility, and therefore 
of the most frequent vibration, commonly have the 
greatest activity. On the number of impulses a ray can 
communicate in a given period of time depends its pow- 
er of destroying the constitution of any group of atoms; 
and the phenomena of interference arising from the su- 
perposition of wave motions occur exactly as might 
have been predicted. 

3d. The direction of wave motion, as involved in the 
idea of polarization, whether plane or circular, seems to 
exert no effect. 



LECTURE XXIV. 

Photography. — Origin of. — Daguerre and Talbot. — 
The Dagxterreotype. — Prof. Draper first takes Por- 
traits from Life. — The Collodion Process. — Nega- 
tives and Positives. — The Albumen Paper Process. — 
Toning and Permanency . — Pry Collodion Processes. 
— Formidas for Collodion, the Nitrate Bath, Devel- 
oping Solution, Fixing Solution. 

Photography, literally, writing by light, is a crea- 
tion of the present century, although many facts that 
might have led to its cultivation were known in the 
Middle Ages. The first germ is to be found in observ- 
ations on the darkening of the chloride of silver by the 
sunlight; and the first photographs, truly speaking, 

What effect has the intensity of the ray? Which rays hare the 
greatest decomposing power ? What is the effect of polarization in 
decompositions? What is the meaning of the term Photography? 
What are some of the early facts in photography ? 



120 THE DAGUERREOTYPE. 

were those made by Wedgewood, who exposed leather 
soaked in nitrate of silver to the sun under the slide of 
a magic lantern. In 1835 Prof. Draper used bromide 
of silver and other sensitive compounds for investiga- 
ting the solar spectrum. 

In 1839 Daguerre announced the discovery of a 
means of fixing the images of the camera obscura, and 
about the same time Talbot, in England, did the same. 
The process of the former, known as the daguerreotype, 
involves the use of a silver-plated sheet of copper, 
which, having been carefully cleaned with rotten-stone 
and a buff, is exposed to the vapors of iodine. It be- 
comes tinged yellow, red, blue, gray, depending on the 
time of the exposure to the vapor, but is most sensitive 
when yellow. In that condition it is exposed in the 
camera obscura to the image of some object, being care- 
fully preserved from extraneous light. The latent im- 
age has then to be developed by the aid of vapor of 
mercury rising from a portion of that metal heated to 
170°. In about four minutes the image is fully brought 
out, if the camera exposure has been sufficient, and it is 
then only necessary to dissolve away the remainder of 
the film of iodide of silver to prevent farther change. 

The process of Daguerre was very sluggish, and was 
generally regarded as only suitable to the reproduction 
of still objects; but soon after its publication Prof. 
Draper succeeded in taking portraits from life, and ar- 
rived at such a degree of excellence at once that those 
pictures have scarcely been surpassed since. 

The great subsequent improvements of the process 
were the discovery of the use of bromine as an acceler- 
ating agent, and that of the process of gilding, for fix- 
ing the image by covering it with an extremely thin 
film of gold, deposited from a solution of the chloride 
of gold in hyposulphite of soda. 

The daguerreotype image consists in the whites of an 
amalgam of silver, and in the dark parts of the un- 
changed silver. Prof. Draper showed that this amal- 
gam presents a dotted or stippled arrangement, and 

Describe the daguerreotype process. Who took the first portraits 
from life ? State some of the subsequent improvements in the da- 
guerreotype process. What is the nature of the daguerreotype 
image ? 



THE COLLODION PROCESS. 121 

may be copied by isinglass, and the original in this way 
reproduced. 

Talbot's process has never come into general use, ex- 
cept for enlarged pictures on paper, being entirely su- 
perseded by the Collodion process. This process, in- 
vented by Scott Archer, depends on the fact that gun- 
cotton, or pyroxyline, is soluble in alcohol and ether, 
and affords, on drying, a clear and tenacious film. Such 
collodion, containing some soluble iodide or bromide, 
or both, is poured on a clean glass plate, and, when set, 
-is immersed in a bath of nitrate of silver, which changes 
the iodide and bromide into iodide and bromide of sil- 
ver. In this state.it is exposed to light, and, after a 
sufficient lapse of time, the invisible image is developed 
by pouring over the plate a solution of pyrogallic acid, 
or protosulphate of iron, slightly acidified. This causes 
a reduction of metallic silver in the black state on all 
those parts which have received the impression of light, 
the amount of deposit being greater as the light was 
greater. 

After washing in water, the plate is soaked in hypo- 
sulphite of soda, or cyanide of potassium, to get rid of 
the iodide and bromide of silver, and is then again 
washed and dried. On being varnished, the negative 
thus produced may be used for printing on paper. 

If the exposure to light be made shorter, and the de- 
velopment not pushed so far, on placing behind the re- 
sulting picture a blackened surface, a positive is seen, 
in which the lights and shades are not reversed, as in 
the negative. Very many forms of these pictures are 
produced, and many names, as ambrotype, melainotype, 
have been introduced to distinguish them. 

The great superiority of the collodion process results 
from the fact that negatives can be used to multiply in- 
definitely copies of the original. The albumen process 
on paper, by means of which this multiplication is ef- 
fected, is conducted as follows. 

A sheet of paper, which is free from metallic grains 
or other impurities, is floated on the surface of a bath 
consisting of albumen that has been thoroughly beaten 

Describe the collodion process. Why is the collodion plate soaked 
in hyposulphite of soda? What is the difference between a positive 
and a negative? Describe the albumen process on paper. 

F 



122 PAPER POSITIVES. 

up and filtered, containing chloride of ammonium. 
After the paper has dried, it is floated in a strong solu- 
tion of nitrate of silver, which causes the production of 
chloride of silver, and coagulates the albumen. As 
soon as dry, the paper is exposed behind a negative to 
either sunlight or daylight. The operator judges of the 
time required by the darkness of tint assumed by the 
chloride. The paper has next to be soaked in water, 
and then toned. 

The object of the toning operation is to replace the 
reduced silver by gold, and thereby change the reddish 
color of the print to a shade either of purple, brown, or 
black. The tpning-bath may be composed of many va- 
rious substances ; one of the best, however, is a solu- 
tion of chloride of gold, rendered neutral by carbonate 
of lime, and containing a small quantity of chloride of 
lime. This rapidly produces a beautiful color, and is 
the one used by the author in taking his photographs 
of the moon. 

The next step is to remove the superfluous chloride 
of silver by the aid of hyposulphite of soda, and after- 
ward to submit the proof to a current of water to effect 
the removal of the hyposulphite, which, if allowed to re- 
main, would infallibly cause it to turn yellow and fade 
away. 

The permanency of paper positives depends on the 
thoroughness of the toning operation, the gold substi- 
tuted for silver not being liable to sulphurization. The 
early photographs, which have, in the last ten years, so 
nearly passed away altogether, were toned by a bath of 
hyposulphite of soda and chloride of gold ; and although 
their tints were very beautiful in the first instance, yet, 
owing to the sulphide of silver that entered into them, 
they could not be permanent. 

The collodion and paper processes have undergone a 
great number of modifications, in order to adapt them 
to special purposes. Dry plate photography, for exam- 
ple, involves a method of retaining the sensitiveness of 
a collodion film, though the excess of nitrate of silver 
that in the wet process is upon the plate be w T ashed off. 
The desired result is usual ly accomplished by flowing 

What is toning ? What influences the permanence of paper pic- 
tures ? Describe the process of dry plate photography. 



PHOTOGRAPHIC FORMULAS. 123 

upon the collodion film, after it has been taken from the 
nitrate of silver bath and washed, a preservative solu- 
tion of tannin^malt, or some similar substance, which 
permits the film to be subsequently permeated by water 
during its development. These dry processes are of 
great convenience to the landscape photographer, and 
have led to many ingenious forms of apparatus for car- 
rying the plates and introducing them into the camera 
obscura. 
The following formulas are in common use : 

Composition of Iodized Collodion. 

Ether 4 ounces (fluid). 

Alcohol..... 4 ounces. 

Pyroxyline 30 to 60 grains. 

Iodide of Cadmium 50 grains. 

Bromide of Cadmium 6 grains. 

The nitrate of silver bath for negatives is merely a so- 
lution in water of 40 grains to the ounce. 

Developing Solution. 

Protosulphate of Iron 3 ounces. 

Acetic Acid, No. 8 4 ounces. 

Alcohol 3 ounces. 

Water 40 ounces. 

Or, 

Pyrogallic Acid 1J grains. 

Alcohol 1 drach m . 

Acetic Acid, No. 8 1 drachm. 

Water 1 ounce. 

Fixing Solution. 

Cyanide of Potassium 1 drachm. 

Water 4 ounces. 

Or, 

Hyposulphite of Soda 6 ounces. 

Water 16 ounces. 

What is the use of £he tannin or malt ? What are the advantages 
of this process ? Give the formulas for iodized collodion, the devel- 
oping solution, the fixing solution. 



124 ELECTRICAL PHENOMENA. 



LECTURE XXV. 

Electricity. — First Discoveries in Electricity, — Lead- 
ing Phenomena. — Conductors, Non- Conductors, and 
Insulators. — Tico Kinds of Electricity , Vitreous and 
Resinous, or Positive and Negative. — Paw of Elec- 
trical Attraction and Repulsion. — Plate Machine. — 
Cylinder Machine. — Method of Using. — Miscella- 
neous Experiments. 

More than 2000 years ago it was discovered that 
when amber is rubbed it acquires the property of at- 
tracting light bodies. This incident has served to give 
a name to the agent whose operations we have now to 
explain, which has been called electricity, from rjkeKrpov, 
amber. 

The catalogue of substances in which electrical de- 
velopment can be produced was greatly increased by 
Gilbert, who showed that glass, resin, wax, and many 
other bodies are equally effective as amber. They, too, 
when rubbed, can attract light substances, and, when 
the excitement is vigorous, emit sparks like those which 
are seen when the back of a cat is rubbed on a frosty 
night. 

If a piece of brown paper be thoroughly dried at the 
fire until it begins to smoke, and then rubbed between 
woolen surfaces, it will emit sparks on the approach of 
the finger, attract pieces of paper and then repel them. 
This latter phenomenon is not, however, peculiar to it, 
but is noticed in the case of all highly-excited bodies. 
Electrified bodies therefore exhibit repulsions as well as 
attractions. 

Let there be taken a glass tube, a b, Fig. 85, an inch 

Fig. S6. in diameter and a foot or 

a b more loqg, closed at the 

==Cq ■ -> O g end b by means of a cork, 

into which there is inserted a wire with a round ball, c. 

If the tube be excited by rubbing with a piece of dry 

From what fact does the term electricity originate ? What occurs 
when glass, resin, etc., are rubbed? What phenomena may be ex- 
hibited by brown paper ? Describe Fig. 85. 



CONDUCTORS AND NON-CONDUCTORS. 125 

silk, it may be shown that not only does the space rub- 
bed possess the powers of attraction and repulsion, but 
also the cork and the ball. Nor does it matter how 
long the wire may be ; the electric power is transmit- 
ted through the whole of the metal. A metal, there- 
fore, can conduct electricity. 

But if, instead of a piece of metal, we terminate the 
glass tube with a rod of glass or sealing-wax, or hang 
a ball to it by a thread of silk, in all these cases the 
electric power can not pass. Such substances are there- 
fore non-conductors of electricity. The important fact, 
that all substances may be divided into two classes, con- 
ductors and non-conductors, was first accidentally dis- 
covered by Mr. Grey, who found that all metals and 
moist bodies are conductors, and that glass, resins, wax, 
sulphur, atmospheric air, are non-conductors. The fol- 
lowing table exhibits the relation of bodies in this re- 
spect. The nearer the substance is to the bottom of the 
table, the better is its conducting power. 

Non - Conductors. Spermaceti. 

Dry Gases and Dry Steam. turpentine and Volatile Oils. 

Shellac. Flxed 0lls - 

Sulphur. String and Vegetable Fibres. 

Amber. ' Moist Animal Substances. 

Resins.*' Water. 
Gutta Percha and Caoutchouc. Valine Solutions. 

Diamond. FJa^e. 

gj| k Melted Salts. 

Dry Fur Plumbago. 

Glass. Charcoal. 

j ca All the Metals. 

Conductors. 

When electricity is communicated to a body which 
is supported on any of these non-conducting substances, 
its escape is cut off, and the body is said to be insu- 
lated. 

To Otto Guericke, who was also the inventor of the 
air-pump, we owe another of the most important dis- 
coveries in electricity, that bodies which have touched 
an excited substance are subsequently repelled by it. 
Thus, if we rub a glass tube, «, Fig. 86, until it becomes 
electrified, and then present to it a feather, #, suspended 

What is a non-conductor of electricity ? What is a conductor ? 
Give examples of each. When is a body said to be insulated? 




126 TWO ELECTRICITIES. 

by a silk thread to a stand, c, the feather is 
at first attracted, and then immediately re- 
pelled. 

A very celebrated French electrician, Du- 
fay, having caused a light, downy feather to 
be repelled by an excited glass tube, intend- 
ed to amuse himself by chasing it round the 
db room with a piece of excited sealing-wax. 

To his surprise, instead of being repelled, the feather 
was at once attracted. On examining the cause of this 
more minutely, he arrived at the conclusion that there 
are two species of electricity, the one originating when 
glass is excited, and the other from resin or wax. To 
these he gave the names of vitreous and resinous elec- 
tricity, thus pointing out their origin. They are also 
called positive and negative electricities. 

He found that these different electricities possess the 
same general physical qualities : they are self-repulsive, 
but the one is attractive of the other. This is readily 
proved by hanging a feather by a linen thread to the 
prime conductor of the electrical machine, and, when it 
is excited, bringing near to it an excited glass tube. 
The feather is already vitreously electrified, and the 
tube, being in the same condition, at once repels it. 
But a stick of excited sealing-wax, being resinously 
electrified, that is to say, in the opposite condition to 
the feather, at once attracts it. 

These various results may all be grouped under the 
following general law, which includes the explanation 
of a great many electrical phenomena. Bodies electri- 
fied dissimilarly attract, and bodies electrified similar- 
ly repel. Like electricities repel, unlike ones attract. 

For the sake of observing electrical phenomena more 
readily, instruments have been invented called electrical 
machines. They are of two kinds, the plate machine 
and the cylinder. They derive their names from the 
shape of the glass employed to yield the electricity. 
The plate machine, Fig. 87, consists of a circular plate 
of glass, a a, which can be turned upon an axis, b, by 

Describe Fig. 86. Describe Dufay's discovery. What conclu- 
sion did Dufay arrive at? What is the difference between vitreous 
and resinous electricity ? W x hat is the general law of attraction and 
repulsion ? Describe the plate machine. 



ELECTRICAL MACHINES. 



127 




Fig. 88. 



means of a winch, c ; at d is a 
pair of rubbers, which com- 
press the glass between them, 
and a piece of oiled silk ex- 
tends over the glass plate, as 
shown at e. In the same man- 
ner, on the opposite side of the 
plate, there is another pair of 
rubbers, c?, and an oiled silk, e ; 
f\% the prime conductor, Avhich 
.gathers the electricity as the 
plate revolves. It must be sup- 
ported on an insulated stem. 

The cylinder machine is represented in Fig. 88. 
consists of a glass cylin- 
der, a a, so arranged that 
it can be turned on its 
axis by the multiplying 
wheel b b. The rubber 
bears against the glass 
on the opposite side to 
that seen in the figure, 
and the oiled silk is shown 
at c / d is the prime con- 
ductor, usually a cylinder 
with rounded ends, made of thin brass, and e its insu- 
lating support. 

Of these machines the plate is commonly the most 
powerful. It is more liable to be broken than tl^e cyl- 
inder, from the disadvantageous way in which the pow- 
er to turn it round is applied. 

To bring an electrical machine into activity, it must 
be thoroughly dried, but a plate machine should never 
be set before the fire to warm, or it will almost certain- 
ly crack. The rubbers are to be spread over with a 
little Mosaic gold or amalgam of zinc, and the stem of 
the conductor made dry. If the rubbers of the machine 
are not in connection with the ground, there must be a 
chain hung from them to reach the table. Then, when 
the instrument is in activity, on presenting the ringer 

Describe the cylinder machine. Which is the best? How is an 
electrical machine prepared for action ? What occurs on presenting 
the finger to the prime conductor ? 




128 



ELECTRICAL EXPERIMENTS. 



to the prime conductor, a succession of sparks is emit- 
ted, attended by a crackling sound. 

A great many beautiful experiments may be made by 
the aid of this machine. They are, for the most part, 
illustrations of the luminous effect of the spark, attrac- 
tions and repulsions, and certain physiological results, 
as the electrical shock. 

If small pieces of tin-foil be pasted round a glass tube 
Fig. 89. in a spiral form, as shown in 

Qg?s ^/v\/s*ALA* f A Fig. 89, a b c, distances of the 
a & c twentieth of an inch interven- 

ing between, and the ends of the tube terminated by 
balls, on presenting one of these balls to the prime con- 
ductor, and holding the other in tjie hand, as the spark 
passes it has to leap over each interstice between the 
spangles of tin-foil, and exhibits a beautiful spiral line 
of light. 

By pasting the tin-foil on a 
pane of glass in such a way 
as to direct the spark prop- 
erly, words may be written 
in electric light, as shown in 
Fig. 90. 

As the electric spark can not be confounded with 
any other physical phenomenon whatever, its presence 
is always indubitable evidence of 
electric excitement. Thus we can 
prove that electricity may be trans- 
ferred to the human body from the 
machine by placing a man on a stool 
supported by glass pillars, Fig. 91. 
If he touches the prime conductor with one hand, sparks 
may be drawn from any part of his clothing or body. 



Fig. 90. 




Fig. 91. 




Describe Figs. 89 and 90. 
91, demonstrate? 



What does the electrical stool, Fig. 



INDUCTION. 129 



LECTURE XXVI. 



Theory of Electrical Induction. — Phenomena of 
Induction. — Independent of Shape. — Permanent Ex- 
citement by Induction. — Takes place through Glass. 
— Experiments illustrative of Attraction and Pepul- 
sion, and Induction. — Medicated Tubes. 

There are many ways in which electrical excitement 
can be developed. In the common machine it is by 
friction ; in the tourmaline, a crystallized gem, by heat ; 
and in other cases by chemical action, and by conduce 
tion. Electrical disturbance also very often -arises from 
induction. 

By the term electrical induction, we mean that a body 
which is already excited tends to disturb the condition 
of others in its neighborhood, inducing in them an elec- 
trical condition. 

Thus, let a, Fig. 92, be the terminal ball of the prime 
conductor, and a few inches Fiffm 92> 

off let there be placed a sec- 
ondary conductor, b c, of 
brass, supported on a glass 
stand, and at each extremity, 
b and c, of the conductor, let 
there be arranged a pair of 
cork balls, suspended by linen c ^ > 

threads, as shown in the figure. As soon as the ball a 
is electrified by turning the machine, and without any 
spark passing from it to the secondary conductor, the 
balls will begin to diverge, showing that the condition 
of that conductor is disturbed by the neighborhood of 
the excited ball, a. 

It will farther be found, on presenting an excited piece 
of sealing-wax to the pairs of cork balls, that one set is 
attracted and the other repelled. They are therefore in 
opposite electrical states. The disturbing ball is vitre- 
ously electrified, and that end of the secondary conduct- 
or nearest it is resinous, the farther end being vitreous. 

How may electrical excitement be produced ? What is meant by 
electrical induction ? Describe Fig. 92. What occurs to the balls 
on the secondary conductor ? 

F2 




130 



ELECTRICAL INDUCTION. 



Fig. 93. 



+ 1 



fi'i. uifi' l 



If the disturbing ball a be now removed, the electric 
disturbance ceases and the corks no longer diverge. 

The phenomena of electrical induction are not depend- 
ent on the shape of bodies. Let there be two flat cir- 
cular plates, a 5, Fig, 93, supported on 
glass stands, and set a few inches apart, 
looking face to face. Let one of them, a, 
be electrified positively by contact with 
the prime conductor, as indicated by the 
sign +. It immediately induces a change 
in the opposite plate, the nearest face of 
which becomes negative, — , and the more 
distant positive. It is evident that this disturbance is 
a consequence of the law that " like electricities repel, 
and unlike ones attract." In the plate b both species 
of electricity exist ; and a, being made positive, even 
though at a distance, exerts its attractive and repulsive 
agencies on the electric fluid of 5, the negative electrici- 
ty of which it attracts and draws near to it, the positive 
it repels and drives to the farthest side ; so that the dis- 
turbed condition of the body b is a result of the fact 
that a, being electrified positively, will repel positive 
electricity and attract negative. 

Now let the plate b be touched by the finger, or a 
channel of communication opened with the earth ; the 
positive electricity of a, still exerting its repulsive agen- 
cy on that of 5, will drive it into the ground, and b will 
now become negative all over. 

Let b be once more insulated by breaking its commu- 
nication with the ground, and let a be removed ; it will 
now be found that b is permanently electrified, and in 
the opposite condition to a. 

Fig. 94. By manipulating in this manner, we can 

therefore effect a permanent disturbance in 
the condition of an insulated body by bring- 
ing an excited one in its neighborhood. 

In these changes the intervention of a piece 
of glass makes no difference. Let a circular 
plate of glass, a, Fig. 94, be set so # as to in- 
tervene between the metallic plates a and b, 

What is their electrical state respectively ? . Does the shape of a 
body influence induction ? Describe Fig. 93, and its method of ac- 
tion. How may the plate b be permanently electrified? 




ELECTRICAL EXPERIMENTS. 



131 




and still all the phenomena occur as before. Electrical 
induction, therefore, can take place through glass. 

On the principles of induction, and of electrical at- 
traction and repulsion, many interesting experiments 
may be explained. The following may serve as exam- 
ples : To the ball of the prime conductor let there be 
suspended a circular plate of brass, a, Fig. 95, six inches 
in diameter; horizontally and beneath it let Fig. 95. 
there be another plate, 5, supported on a con- 
ducting foot parallel and at a distance of three 
-or four inches. On the lower plate b place 
slips of paper or other light substance, cut into ^ 
the figure of men or animals. On setting the 
machine in motion so as to electrify the upper 
plate, the objects move up and down with a 
dancing motion. The cause is obvious: the 
plate a, being positive, repels by induction the positive 
electricity of the figures through the conducting stand 
into the earth, and they thus, being rendered negative, 
are attracted by the upper plate. On touching it they 
become electrified positively like it, and th^i are repel- 
led, and fall down to discharge their electricity into the 
ground, and this motion is continually repeated. 

Upon a horizontal brass bar, a b, Fig. 96, three bells 
are suspended, the outer ones at a 
and b by chains, the middle one at c 
by a silk thread. Between the bells 
the metallic clappers d and e are sus- 
pended by silk, and from the centre 
bell the chain f extends to the table. 
On hanging the arrangement, by the 
hook at g, to the excited prime conductor, the bells ring, 
the clappers moving from the out- 
er to the central bell and back, 
alternately striking them. 

On a pivot, a, Fig. 97, suspend 
a bell jar having four pieces of 
tin-foil pasted on its sides b c d. 
Connect the jar, by means of the 
insulated w T ire ?/, with the prime 

What effect has the intervention of glass ? Describe the dancing 
figures experiment. What is the cause of the motion? Describe 
Fig. 96. Describe the rotating jar, Fig. 07 



Fig. 96. 




Fig. 97. 




132 ELECTEICAL EXPERIMENTS. 

conductor, so that the pieces of tin -foil may receive 
sparks. On the opposite side arrange a conductor, "#, 
in connection with the ground by a chain. On putting 
the machine into activity, the jar will commence rotating 
on its pivot. 

Take a cake of sealing-wax or shellac eight or ten 
inches in diameter, electrify it by friction with a piece 
of flannel, and receive on its surface a few sparks from 
the prime conductor by bringing it near the ball. Then 
blow upon its surface, from a small pair of bellows, a 
mixture of flowers of sulphur and red lead which have 
been intimately ground together in a mortar. This 
mixture is of an orange color ; but, the moment it im- 
pinges on the cake, it is, as it were, decomposed, the 
yellow sulphur settling on one portion and the red lead 
on another, giving rise to very curious and fantastical 
figures, called Lichtenberg's figures. 

Soon after electricity became a subject of popular at- 
tention, it was currently believed that if medicines of 
various kinds were sealed up in glass tubes and the 
tubes electrically excited, their peculiar virtues would 
be exhaled in such a manner as to impress the patient 
with their specific purgative, emetic, or other powers. 
Like many of the popular delusions of our times, this 
imposture was supported by the most cogent evidence, 
and maladies cured publicly all over Europe. Like 
them, th?se " medicated tubes" have served to prove 
the worthlessness of human testimony w T hen derived 
from the prejudiced and ignorant. 

It should be remarked that, in their action upon ma- 
terial bodies, electricity and heat differ greatly. The 
former has no kind of influence in determining magni- 
tude, whereas the size of any object depends on its 
temperature. 

How are Lichtenberg's figures produced? What are medicated 
tubes ? What is the difference between heat and electricity in their 
action on bodies ? 



DISTRIBUTION OF ELECTRICITY. 133 



LECTURE XXVII. 

Laws of the Distribution of Electricity, and The- 
ories of Electricity. — Distribution of Electricity. 
— On a Sphere and Ellipsoid. — Action of Points. — 
Franklirts Discovery of the Identity of Electricity 
and Lightning. — Lightning Rods. — The Two Elec- 
trical Theories, Franklin's and Dufay's. — Electrici- 
ty is a Compound Force. — The Ley den Jar. — Dis- 
charging Bod. — Electric Battery. 

When electricity is communicated to a conducting 
body, it does not distribute itself uniformly through the 
whole mass, but exclusively upon 
the surface. Thus, if to the spher- 
ical ball a, Fig. 98, supported on an 
insulating foot, 5, there be adjusted 
two hemispherical caps, c c, also on 
insulating handles, it may be proved 
that any electricity communicated 
to a distributes itself entirely upon the surface ; for if 
we place upon a the caps c c, and then remove them, it 
will be found that every trace of electricity has disap- 
peared from «, and has accumulated upon the caps, 
which, while they were upon the ball, formed its su- 
perficies. 

Again, if we take a large brass ball, a, Fig. 99, sup- 
ported on an insulating stand, and having on 
its upper portion an aperture, 5, through which 
we may have access to the interior, it will be 
found, on examination, that the most delicate 
electrometers can discover no electricity with- 
in the ball, the whole of it being on the exter- 
nal superficies. 

In the case of a spherical body, not only is 
the distribution entirely superficial, but it is 
also uniform. Each portion of the sphere is electrified 
alik^ But where, instead of a spherical, Ave have an 

Upon what part of a body does electricity distribute itself? How 
may this be proved ? What does Fig. 99 prove ? What is the dis- 
tribution on a sphere? 





134 DISTRIBUTION OP ELECTRICITY. 

Fig. 100. ellipsoidal body, it is different. Thus, 

-^ if we examine the condition of such 

## | „^| c a conductor, Fig. 100, the quantity 

^^^^ of electricity in its middle portion, 
\d as at a d, will be the smallest, and 

it will increase as we advance to- 
ward the ends, b c. In different 
ellipsoids, as the length becomes 
greater, so the amount of electricity 
found on the extremities is greater. When, therefore,, 
a conductor of an oblong spheroidal shape is used, the 
intensity of the electricity at the extremity of the two 
axes, a d and b c, Fig. 100, is exactly in the proportion 
of the length of those axes themselves ; and should the 
disproportion in the length and breadth of the conduct- 
ing body be very great, as in the case of a long wire 
or other pointed body, a very great concentration will 
take place upon the points. On this principle we ex- 
plain the effect of pointed bodies on conductors. If the 
prime conductor of the machine have a needle or pin 
fixed upon it, the electricity escapes away into the air 
visibly in a dark room ; and in the same way, if pointed 
bodies surround the electrical machine, it can not be 
highly excited, as they rapidly take the charge from its 
conductor. 

These principles may be very w^ell illustrated by tak- 
ing a long strip of tin-foil, so arranged as to be rolled 
and unrolled upon a glass axis, and connected w T ith a 
pair of cork balls, the divergence of w T hich shows its 
electrical condition. If now to this, when coiled up, a 
sufficient amount of electricity is communicated to make 
the balls diverge, on pulling out the tin-foil so as to 
have a larger surface they will collapse, but on winding 
the foil up again they will again diverge, showing that 
the distribution of electricity is wholly superficial, and 
that when a given quantity is spread over a large sur- 
face, it necessarily becomes weaker in effect. 

At a very early period electricians had observed the 
close similarity between the phenomena of the electric 

What is the distribution on an ellipsoid ? What is the diminu- 
tion on a wire? What is the effect of pointed bodies on conduct- 
ors ? How may the distribution of electricity be shown by a coil of 
tin-foil ? 



THEORIES OF ELECTRICITY. 135. 

spark and those of lightning, but in the year 1752 Dr. 
Franklin proved that they were identical. He was 
waiting for the erection of the spire of a church in Phil- 
adelphia, on the extremity of which he intended to raise 
a pointed metal rod, with a view of withdrawing the 
electricity from the clouds, when the accidental sight of 
a boy's kite suggested to him that ready means of ob- 
taining access to the more elevated regions of the air. 
Accordingly, having stretched a silk handkerchief over 
a light wooden cross, and arranged it as a kite, he at- 
tached to it a hempen string, terminating in a silk cord, 
and, taking advantage of a thunder-storm, raised it in 
the air. For a time no result w r as obtained; but the 
string becoming w T et with the rain, and thereby rendered 
a better conductor, he perceived that the filaments 
which hung upon it repelled one another, and on pre- 
senting his knuckle to a key w r hich had been tied to the 
end of the hempen string, received an electric spark.. 
The identity of electricity and lightning was proved. 

Franklin soon made a useful application of his discov- 
ery. He proposed to protect buildings from the effects 
of lightning by furnishing them with a metallic rod, 
pointed at its upper extremity and projecting some feet 
above the highest part of the building, and continuously 
extending downward until it was deeply buried in the 
ground. This contrivance, the lightning-rod, is now, as 
is well known, extensively applied. 

There are two theories respecting the nature of elec- 
tricity : 1st. Franklin's theory, which assumes that there 
is but one fluid ; and, 2d. Dufay's theory, which assumes 
that there are two fluids. 

Franklin's theory is that there exists throughout all 
space a subtle and exceedingly elastic fluid, called the 
electric fluid, the peculiarity of which is that it is repul- 
sive of its own particles, but attractive of the particles 
of other matter ; that there is a specific quantity of this 
fluid, which bodies are disposed to assume when in a 
natural condition or state of equilibrium, and that if we 
communicate to them more than their natural quantity 

Describe Franklin's discovery of the identity of lightning and 
electricity. What use did he make of the discovery? What theo- 
ries are there of the nature of electricity ? What is Franklin's the- 
orv ? 



136 THEORIES OF ELECTRICITY. 

they become positively electrified, or if we take away a 
portion of that which is natural to them they become 
negatively electrified. 

Dufay's theory is that there exists throughout all 
space a universal medium, the immediate properties of 
which are not known. It is composed of two species 
of electricity, the positive and the negative, each of these 
being self-repellant, but attractive of the other kind. 
Bodies are in a neutral or natural state or condition of 
equilibrium when they contain equal quantities of the 
two electricities; they are positively electrified when 
the positive is in excess, and negatively when the nega- 
tive is in excess. 

Electricity is, however, now coming to be regarded 
as a compound force, remarkable for the peculiar form 
of action and reaction that it exhibits. This kind of 
action and reaction follows the same law of equality 
.and opposition in its manifestations as that which is 
shown more obviously in the phenomena of mechanics. 
Whenever vitreous electricity appears at one point, a 
corresponding amount of resinoug electricity is invaria- 
bly developed in its vicinity, reacting against it, and 
thus enabling its presence to be recognized. 

As one kind of electricity can never make its ap- 
pearance alone, but is always accompanied by an equal 
quantity of the other, we uniformly find that the rubber 
and the surface rubbed are in opposite states ; if the 
one is positive, the other is negative. It is on this 
principle that many machines are furnished with means 
of collecting from the prime conductor or the rubber, 
Fig. 101. and therefore of obtaining the positive or 
negative electricity at pleasure. 

In 1745 the Leyden jar was discovered. 
This consists of a glass jar, Fig. 101, coated 
on its inside with a piece of tin-foil within 
an inch or two of its upper edge, and also 
on its outside to the same point. Through 
the cork which closes the mouth of the jar 
a brass rod, terminated by a ball, passes. 
-**' The rod reaches down to the inside coating 

What is Dufay's theory ? What is the present view of the nature 
of electricity ? Can one kind of electricity alone be produced ? De- 
scribe the Leyden jar. 




THE LEYDEN JAR. 



137 



and touches it. On holding this instrument by the ex- 
terior coating and presenting its ball to the prime con- 
ductor, a torrent of sparks passes into the jar ; and when 
it is fully charged, if, still retaining one hand in contact 
with the outside, we touch the ball, a bright spark pass- 
es with a loud snapping noise, and the operator receives 
through his arm and breast what is called the electric 
shock. 

If w r e take the discharging rod, Fig. 102, consisting 
of two brass arms, a a, terminated by balls work- ^.102. 
-ing on a joint, 5, and supported by an insulating 
handle, c, by bringing one of its balls in contact 
with the outside coating of a Leyden jar, and its 
other ball with the ball of the jar, the discharge 
will take place as before, but the operator, pro- 
tected by the glass handle, receives no shock. 

If between the outside coating of the jar and 
one of the balls of the discharging rod a piece of 
cardboard be made to intervene and the spark 
passed, the card will be found to be perforated, a 
burr being raised on both sides of it as though two 
threads had been drawn through the hole in opposite 
directions at the same time; 
and from this an argument in 
favor of the theory of two fluids 
has been drawn. 

When a great number of jars 
are connected together, so that 
all their inside coatings unite, 
and all their outside coatings 
are also in contact, they consti- 
tute what is termed an electric 
battery, as seen in Fig. 103. 
By this instrument many of the 
more violent effects of electrici- 
ty may be illustrated, such as the splitting of pieces of 
wood, and the ignition and dispersion of metallic wires. 

How is it used ? Describe the discharging rod ? How may a 
card be perforated by the spark ? What is the peculiarity of the per- 
foration ? What is an electric battery ? 



Fig. 103. 




138 THE LEYDEN JAR. 



LECTURE XXVIII. 

Electrical Instruments and Faraday's Theory of 
Electric Polarization. — Theory of the Ley den 
Jar. — Electrometers : Quadrant, Gold-leaf Torsion, 
Peltier's. — Bohnenberger^s Electroscope. — ZanibonVs 
Pile. — Faraday's Theory of Polarization. — Specific 
Induction. — Methods of Discharge by Conduction, 
Disruption, Convection. — TJie Brush. — Hydro -elec- 
tric Machine. 

The office which is discharged by the metallic coat- 
ings of a Leyden jar is illustrated by the apparatus 
Fig. 104. It consists of a conical glass jar, to the inte- 
Fig. 104. rior and exterior of which movable coatings 
of thick tin plate are adapted, the interior one 
having a rod and ball projecting from it. This 
may be charged like any other Leyden vial; 
but, on taking off its outside coating and re- 
moving its interior, they may be handled and 
brought into contact with each other, and no 
spark passes; but, on restoring them to their 
former position, and applying the discharging rod, the 
jar is discharged. They therefore only serve to make 
a complete conducting communication between all parts 
on the interior and all on the exterior of the jar. 

The condensing action of the Leyden vial, which en- 
ables it to hold so large a quantity of electricity, is due 
to induction. When the inner coating is brought into 
contact with the prime conductor, it participates in its 
electrical condition. We may therefore suppose it to 
be positively electrified. The positive electricity of the 
interior repels that of the exterior -into the earth, the 
outside of the vial being in communication with the 
ground. It therefore appears that the inner coating is 
positive, the outer negative, and the whole jar, taken to- 
gether, is in the neutral condition. The inner coating, 
continuing to receive a farther charge from the prime 
conductor by induction through the glass, continually 

What is Fig. 104 intended to demonstrate? How is it used? 
What is the condensing action of the Leyden jar due to? 




ACTION OF THE LEYDEN JAR. 



139 



Fig. 105. 



repels more of the same kind, the jDOsitive into the 
ground and the negative accumulates on the outside. 
In this manner an indefinite quantity might be accumu- 
lated, were it not for the fact that, owing to the distance 
which intervenes between the two coatings by reason 
of the thickness of the glass, the quantity of positive 
electricity in the interior is never precisely neutralized 
by the quantity of negative on the exterior, for all in- 
ductive actions enfeeble as the distance increases. The 
jar eventually refuses to receive any more sparks from 
the machine. 

Although, in charging a jar, the interior coating is 
commonly brought into contact with the prime conduct- 
or, yet the charging may be equally well accomplished 
if the external coating receive the sparks, provided only 
that the interior communicates with the ground. 

The action of the Leyden vial may be illustrated by 
the following experiments, With- 
in an inch of the ball, <2, of the 
prime conductor, Fig. 105, bring 
a secondary conductor, 5, sup- 
ported on an insulated stem, c, 
and on putting the electrical ma- 
chine in activity, two or three 
sparks will pass from a to-#, but 
after that no more. The cause of the refusal on the 
part of the secondary conductor to receive any farther 
charge is obviously due to the fact that the electricity 
which is already communicated to it repels that upon 
the ball a, and prevents the passage of Fi 106 

any more. 

If now we take a Leyden jar, 5, Fig. 
106, and, having insulated it on a stand, 
bring it within a short distance of the 
ball, a, of the prime conductor, it, in 
the same manner, will only receive a 
few sparks. But if w T e place a conduct- 
or, c, which is connected with the 
ground, near the outside coating, it will 

Describe the charging of a Leyden jar. Why is there a limit to 
the charge ? What other method of charging may be used ? How 
does Fig. 105 illustrate the action of the Leyden jar? Describe the 
experiment illustrated by Fig. 106. 




140 



THE ELECTEOMETEK. 



Fig. 107. 



be found that for every spark that passes between a 
and &, one passes between the outside coating and c, 
and the sparks follow each other in rapid succession 
until the jar becomes fully charged. From this, there- 
fore, we gather that, while positive electricity is passing 
into the interior of the jar, it is escaping from the exte- 
rior, and that the reason the jar condenses is because its 
sides are in opposite conditions, the positive electricity 
of the interior being nearly neutralized by the negative 
electricity of the exterior. 

Electrometers, or electroscopes, are instruments for 
measuring the intensity of electrical excitement. The 
cork balls which are represented in Fig. 92 are one of 
the most simple of these contrivances. The distance to 
which they will diverge is a rough measure of 
the intensity of the electrical force. The quad- 
rant electrometer depends essentially on the 
same principles. It consists of an upright stem 
of wood, Fig. 107, to which is affixed a semicir- 
cular piece of ivory, from the centre of which 
there hangs a light ball of cork playing on a 
pivot. When this instrument is placed on the 
prime conductor, or other electrified body, the 
stem participates in the electricity, and repels 
the cork ball which hangs in contact with it. 
The amount of repulsion may be read off on the gradu- 
ated semicircle. But no quantity of electricity can ever 
drive it beyond 90° ; and, indeed, its degrees are not 
proportional to the quantities of electricity. 

The gold-leaf electrometer, Fig. 108, 
consists of a glass cylinder, a, in which 
two gold leaves are suspended from a 
conducting rod, terminated by a ball 
or plate, b. On the glass opposite the 
leaves pieces of tin-foil are pasted, so 
that when the leaves diverge fully they 
may discharge their electricity into the 
ground. This is a very delicate instru- 
ment for discovering the presence of 
electricity, but the torsion electrometer of Coulomb is 

What is an electrometer? What is the most simple of these con- 
trivances ? Describe the quadrant electrometer. Describe the gold- 
leaf electrometer. 




Fig. 103. 




ELECTROMETEES. 



141 



Fig. 109. 




to be preferred when it is required to have exact meas- 
ures of that quantity. 

Coulomb's electrometer consists of a glass cylinder, 
A, Fig. 109, upon the top of which 
there is fixed a tube, B, in the axis 
of which hangs a glass thread, 5, 
to the lower end of which a small 
bar of shellac, b d, with a gilt pitk 
ball at one extremity, is fastened. 
Through an aperture in the top of 
:the glass cylinder another shellac 
rod, 6, with a gilt ball, may be in- 
troduced. This goes under the 
name of the carrier. 

If now the lower ball of the car- 
rier be charged with the electricity 
to be measured, and introduced 
into the interior of the cylinder, as 
seen in the figure, it will repel the 
movable ball. By taking hold of 
the button, a, to which the upper end of the glass 
thread, 5, is attached, we may, by twisting the glass 
thread, forcibly bring the carrier ball and movable ball 
into contact. The number of degrees through which 
the thread requires to be twisted represents the amount 
of electricity. To the button, a, an index and scale, c, 
are attached. By this we can tell the number of de- 
grees of twist or torsion which have been given "to the 
thread. These angles of torsion are exactly proportion- 
al to the quantities of electricity. 

Another very convenient electrometer 
was invented by Peltier, in which the di- 
rective force of a small magnet is substi- 
tuted for the torsion of a glass thread. 

One of the most delicate electroscopes 
is that of Bohnenberger. It consists of 
a small Zamboni's pile, a 5, Fig. 110, sup- 
ported horizontally beneath a glass shade, 
and from its extremities, a £, curved 
wires pass, which terminate in parallel 

Describe Coulomb's electrometer. How is Coulomb's instrument 
used? Describe Peltier's electrometer. How is Bohnenberger's 
electroscope arranged? 



Fig. 110. 




142 



ZAMBONI S PILE. 



plates, £> m. One of these is therefore the positive, and 
the other the negative pole of the pile. Between them 
there hangs a gold leaf, d g, which is in metallic com- 
munication with the plate o n by means of the rod c. 
If the leaf hangs equally between the two plates, it is 
equally attracted by each, and remains motionless ; but 
on communicating a trace of electricity to the plate o n, 
the gold leaf instantly moves toward the plate which 
has the opposite polarity. 

Zamboni's electrical piles are made by pasting zinc- 
foil on one side of a sheet of paper and' coating the other 
with finely-powdered peroxide of manganese and honey, 
and then punching out a number of circular pieces half 
an inch in diameter. If several thousands of these be 
packed together in a glass tube so that the zinc faces all 
look in one direction and the manganese in the other, 
and be pressed tightly together by metallic plates at 
the ends, it will be found that one extremity of the pile 
is positive and the other negative. With a dry pile of 
20,000 pairs sparks can be obtained, 
and a Leyden vial charged sufficiently 
to give shocks. If the pile be dried it 
loses activity, but otherwise it will con- 
tinue to work for years. Fig. Ill rep- 
resents a pair of these piles arranged so 
as to produce what was at one time re- 
garded as a perpetual motion. Two 
piles, a b, are placed in such a position 
that their poles are reversed, and be- 
tween them a ring or light ball, <?, vi- 
brates like a pendulum on an axis, d. 
It is alternately attracted to the one and then to the 
other, and will continue its movements for years. It is 
covered by a glass shade. 

Many of the fundamental phenomena of electricity 
have been explained by Faraday upon the hypothesis 
that induction is an action of polarization taking place 
in the contiguous molecules of non-conducting media, 
and propagated in curved lines. Bodies susceptible of 
this polarization are termed dielectrics, for they allow 



Fig. 111. 




How are Zamboni's piles made? Describe Fig. 111. What is 
Faraday's explanation of induction ? What are dielectrics ? 



FARADAY'S THEORY OF INDUCTION. 



143 



electric power to traverse them, but by a process differ- 
ing from conduction. As examples, air, resin, glass, and 
sulphur may be mentioned. 

Whatever may be the form or constitution of bodies, 
an electric charge can not be given to them without at 
the same time giving a charge of the opposite kind, but 
of the same amount, to them or other bodies in their vi- 
cinity. This charge is not confined upon their surfaces 
by the pressure of the atmosphere, but through the po- 
larization of the aerial or solid particles of the surround- 
ing dielectrics, producing in them a charge of the same 
amount, but of an opposite kind. Thus, if a positively 
electrified ball be placed in the centre of a hollow me- 
tallic sphere, the intervening space being filled with at- 
mospheric air, the charge is not retained upon the ball 
by the pressure of the air, but because each aerial parti- 
cle assumes by induction a polarity of the opposite kind 
on the side nearest the ball, and of the same kind on the 
side farthest off. This state of force is therefore com- 
municated to the interior of the hollow sphere, which is 
electrified to the same amount, but of an opposite kind 
to the ball. 

That this polarization takes place is shown by the po- 
sition which small silk fibres or spangles of gold assume 
when placed in oil of turpentine, through which induc- 
tion is established. Each particle disturbs not merely 
*hat which is before or behind it, but it is in an active 
relation w^ith all surrounding it ; and hence the polarity 
can be propagated in curved lines, and induction take 
place around corners and behind obstacles. 

On these principles we can easily account for the dis- 
tribution of electricity on spherical or ellipsoidal con- 
ductors, the repulsion of bodies similarly electrified, the 
condensing action of the Leyden vial, and many other 
similar phenomena. 

By a variety of experiments, Faraday has proved that 
inductive action takes place in curved lines, the direc- 
tions of which can be varied by the approach of bodies. 
He has also shown that the particles of solids, as shellac, 

Mention some examples. What occurs when a body receives an 
electric charge? Describe the action of an electrical ball in the in- 
terior of a sphere. How do we know that polarization takes place ? 
Does induction take place only in straight lines ? 



144 



SPECIFIC INDUCTIVE CAPACITY. 



glass, etc., assume this character of polarity. Non-con- 
ducting bodies, dielectrics, through which the action of 
induction takes place, have each a specific inductive ca- 
pacity. Thus, if three metallic plates, a b c, Fig. 112, be 
insulated parallel to each other, atmos- 
pheric air intervening between a and 5, 
and a plate of* shellac between b and c, 
the shellac will be found to allow induc- 
tion to take place across it twice as readi- 
ly as air. The following table exhibits 
the specific inductive capacity of various 
bodies : 

Specific Induction. 




Air 1.00 

Kesin 1.77 

Pitch 1.80 

Beeswax 1.86 



Glass 1.90 

Sulphur 1.93 

Shellac 1.95 




All gases have the same induc- 
tive capacity, whatever their den- 
sity, elasticity, temperature, or hy- 
grometric condition may be. Fara- 
day's apparatus for this investiga- 
tion was a kind of Leyden vial, 
Fig. 113, consisting of two metal- 
lic spheres, A A, insulated from 
each other by a stem of shellac, B. 
The interval between the two could 
be filled with any gaseous medium 
through the stopcock S. Two of 
the jars were used, one containing 
air as a standard. When the other 
jar was charged, the charge was di- 
vided with that containing air, and 
the relative intensity measured by 
an electrometer. 

After the electric equilibrium of 
a body has been disturbed, it may 
be restored by conduction, disrup- 
tion, or convection. An example 



What is meant by specific inductive capacity ? Give the induc- 
tive capacities of air, resin, etc. What is the case with gaseous bod- 
ies ? Describe Faraday's apparatus. 



HEAT DEVELOPED BY ELECTKICITY. 145 

of the first and second methods of discharge is seen in 
the use of a discharging-rod applied to a Ley den vial, 
the electricity passing quietly along the metallic con- 
ductor a part of the way, but bursting through the in- 
terval of air by disruption. Heat is evolved by the 
passage of electricity along a conductor, the amount in- 
creasing as the resistance from imperfect conduction in- 
creases. 



Development of Heat by Electricity. 

Iron...., 30 

Tin 36 

Lead 72 



Copper 6 

Silver 6 

Gold 9 

Zinc 18 

Platinum 30 



Brass 18 

Tin 1, Lead 1 54 



The amount of heat increases as the square of the 
quantity transmitted in equal times. If the size of the 
conductor be sufficiently reduced, it may be deflagrated. 
In a disruptive discharge particles of the solid conduct- 
ors are torn off by the spark, and, being ignited, give a 
tint to the light. In this way the spectra of many met- 
als have been observed. Not only light, but also heat is 
produced in this method of discharge, as may be shown 
by pasting a slip of tin-foil on glass, and, having cut it 
across in two or three places, laying wafers thereon. 
On passing a discharge, the wafers will be thrown off 
by the expansion produced in the air by heat at those 
points. 

The velocity of movement of the spark greatly ex- 
ceeds that of light, passing through a copper wire at 
the rate of 288,000 miles in a second. Its duration is 
estimated at less than the millionth of a second. Trees 
agitated violently by the wind, if illuminated at night 
by lightning, seem to be perfectly at rest. The distance 
through which disruptive discharge will take place va- 
ries with different media, and with their rarefaction. A 
spark will pass through several inches of flame. 

A dilute spark, or brush, occurs when a discharge 
takes place between a good conductor of limited sur- 

How is electric equilibrium restored? When does electricity 
produce heat ? Is the production the same for all metals ? Give 
examples. What is the law of increase of the heat ? What occurs 
during disruptive discharge ? State the velocity of transmission of 
electricity. What is the brush f 

G 



146 THE ELECTROPHORUS. 

face and a bad one of larger surface ; as, for example, 
when a blunt rod discharges into the air. The brush is 
larger from a surface charged vitreously than resinously. 
Discharge by convection is where the charge is fee- 
bler, and the brush is replaced by a tranquil glow. 

Electricity may be produced in large amount by the 
hydro-electric machine, which consists of an insulated 
boiler, from which steam can escape through long tubes. 
The boiler becomes negative, the escaping steam being 
positive. The smallest quantity of oil or turpentine, 
however, reverses these electrical states. 

The electrophorus is an instrument which depends for 
its action on induction, and is of frequent use in chem- 
istry. It consists of a cake of shellac or sealing-wax, 5, 
Fig. 114. Fig. 114, on which is placed a flat me- 

tallic plate, a, with an insulating han- 
dle, c. On exciting b with a piece of 
warm flannel, it becomes negatively 
electric ; and a being placed on it and 
a finger brought near, a negative spark, 
driven from a by the repulsive influence 
of 5, is received. On lifting a by its insulating handle, 
a positive spark is obtained; on putting it down on 5, 
a negative one ; and in this manner we may obtain an 
unlimited number of sparks — positive ones when a is 
lifted, and negative ones when it is down. A little re- 
flection will show that none of this electricity comes 
from the excited cake 5, but is merely the effect of its 
inductive influence on the electric condition of the me- 
tallic plate a. The electrophorus may be used when 
the weather is too damp for the common machine to 
work. 

What is the hydro-electric machine, and how does it act?* De- 
scribe the electrophorus, and its method of action. 





GALVANIC EXPERIMENTS. 147 



LECTURE XXIX. 

Voltaic Electricity. — GalvanVs Discovery. — The 
Simple Voltaic Circle and its Properties. — Direction 
of the Current. — Different Kinds of Combinations. 
— Use of the Sulphuric Acid. — Cause of the Voltaic 
Current. 

In 1790 Galvani observed that if metallic communi- 
cation is made between the muscles and nerves of a re- 
cently killed frog, convulsive movements occur. If two 
different metals are Fig. us. 

used, as copper and 
zinc, the contrac- 
tions are much 
more energetic. If 
the crural nerve, 
JST y Fig. 115, of a 
frog be exposed 

and connected with lISlljEzI-.! - — « 

a piece ot zmc, Z, 

while, the muscles of the thigh, m, are touched with a 
copper wire, (7, nothing occurs as long as the metals are 
kept apart ; but, as soon as they are brought into con- 
tact* ia convulsive movement ensues, and the same is re- 
peated as often as the contact is made. These phenom- 
ena at first went under the name of animal electricity. 

If a piece of zinc and one of silver be placed on op- 
posite sides of the tongue and the overhanging edges 
brought into contact, a metallic taste is perceived In 
the mouth. If the silver be between the upper lip and 
teeth while the zinc is on the tongue, when the metals 
touch a bright flash is seen. 

The branch of electrical science that arose from such 
observations is called Galvanism or Voltaic electricity, 
and its phenomena are those of electricity in motioD. 
Static electricity, which we have previously considered, 
exhibits that force in a motionless state. 

What fact did Galvani discover ? Describe the experiment Fig. 
115. What electrical experiments may be performed in the mouth ? 
What is the difference between static and voltaic electrieitv ? 




148 THE SIMPLE VOLTAIC CIRCLE. 

It is to be admitted, though of that abundant proof 
will soon be given, that water is not a simple but a com- 
pound body ; that it consists of two elements, oxygen 
and hydrogen. It is also to be understood that metal- 
lic zinc may be amalgamated or united with quicksilver, 
by putting it in contact with that fluid metal under the 
surface of dilute sulphuric acid. Strips of zinc thus 
amalgamated exhibit a pure metallic brilliancy. 

A simple voltaic circle may consist of a strip of amal- 
Fig. lie. gamated zinc, z, Fig. 116, an inch wide and 
three or four inches long, and a similar cop- 
per strip, c, immersed in a vessel of water,/', 
slightly acidulated with sulphuric acid. While 
the copper and zinc are kept separated there 
is no action ; but if we take a metallic rod, c?, 
and connect the two together, a series of phe- 
nomena arise. 
First, from the surface of the copper minute bubbles 
of hydrogen gas are evolved. 

Secondly, the plate of zinc rapidly wastes away, and 
on examining the liquid in the cup we discover the 
cause of this waste, for it contains oxide of zinc. Coup- 
ling this fact with the former, we infer that, so long as 
the metallic rod d is in place, water is decomposed, its 
oxygen uniting with the zinc, its hydrogen escaping 
from the copper. On removing the rod c£, all these phe- 
nomena at once cease. ^ 

Thirdly, if, instead of a metallic rod, c?, a rod of glass 
or other non-conductor of electricity be employed, no 
decomposition occurs. This, therefore, indicates that 
the agent in operation is electricity. 

Fourthly, if for the line of communication a piece of 
metal be employed, and we cautiously lift it from the 
zinc or copper plate, the moment the contact is broken 
in a dark room we see a minute spark. It has already 
been observed that the electric spark can not be con- 
founded with any other natural phenomenon. 

Fifthly, if the line of communication be a very slen- 

Is water a simple or a compound body ? What is amalgamated 
zinc? Describe a simple Voltaic circle. What occurs on connect- 
ing the plates? What gas rises from the copper? What happens 
to the zinc ? What occurs on using a glass rod ? How may a spark 
be produced ? 



PHENOMENA OF A SIMPLE CIRCLE. 149 

der platinum wire, as long as it remains in position its 
temperature rises so high that it becomes red-hot, and 
may remain so for hours. Now, recollecting that the 
ignition and fusion of metals take place when they are 
made to intervene between the coatings of a Leyden 
vial, and considering all the facts which have just been 
set forth, we see that the following conclusion may be 
drawn : that in an active simple Voltaic circle water is 
decomposed, its oxygen going to the zinc and its hydro- 
gen to the copper, and that a continuous current of elec- 
tricity accompanies this decomposition, running from 
one metal to the other through the connecting rod. 

The direction of the current is as follows : The elec- 
tricity, leaving the surface of the zinc, passes through 
the liquid to the copper, then moves through the con- 
necting wire back to the zinc, performing a complete 
circuit. Hence the term Voltaic circle. 

Simple Voltaic circles are of several kinds. That 
which we have been considering consists of two differ- 
ent metals, with one intervening liquid, but similar re- 
sults can be obtained with one piece of metal and tw T o 
different liquids. 

In the foregoing experiment we have used dilute sul- 
phuric acid; this acid discharges a subsidiary duty. 
Zinc,* when it oxidizes, is covered with a coating imper- 
meable to water and air. It is this grayish oxide which 
protects the common sheet zinc of commerce from far- 
ther change. When, therefore, a Voltaic pair gives 
rise to a current by the oxidation of its zinc, that cur- 
rent would speedily stop were not the oxide removed 
as fast as it forms. This is done by the sulphuric acid, 
which forms with it a sulphate of zinc, a substance very 
soluble in water, and the metal thus continually presents 
a clear surface to the water. 

As to the immediate cause which gives rise to the 
Voltaic current, there has been a difference of opinion 
among chemical authors. Volta believed that the mere 
contact of the metals was the electromotive source, and 

How may ignition be produced ? What conclusion may be drawn 
from these observations? What is the course of the current? 
What other kinds of Voltaic circles are there ? What is the use of 
sulphuric acid in these combinations ? What did Volta think was 
the cause of the current ? 



150 THE VOLTAIC PILE. 

endeavored to prove by direct experiment that if a 
piece of copper and one of zinc are brought in contact 
and then separated, they become excited, the one posi- 
tively and the other negatively. Upon these principles 
be was led to the discovery of the Voltaic battery, an 
instrument which has revolutionized chemistry. But 
many facts have now indisputably shown that the origin 
of the current is to be sought in the chemical changes 
going on, and that the energy of the current is propor- 
tionate to the chemical activity. In the instance we 
have had under consideration it is due to the decompo- 
sition of water. The direction of the current is, that 
the positive electricity, starting from the more oxidiza- 
ble metal,' traverses the liquid toward the less oxidizable 
metal, and returns to its point of origin along the wire 
joining the two. 



LECTURE XXX. 

Forms oe the Voltaic Battery. — The Voltaic Pile. 
— Cr 'Oio7i of Cups. — Cruickshaiik? s Battery. — Ob- 
ject of Amalgamation. — DanieWs Battery. — Smeds 
Battery. — Groves Battery. — Bnnse?i > s Battery. — 
Voltaic Effects : the Spark, Deflagration of Metals, 
Ignition of Wires, Arc of Flame. — The Electric 
Light. — Fusion of Metals. — Decomposition of Wet- 
ter. — Oxygen and Hydrogen evolved. 

The Voltaic pile used by Volta consisted of a num- 
ber of pairs of dissimilar metals, as zinc, Z, and copper, 
(7, Fig. 117, separated from one another by pieces of 
cardboard or flannel, F, moistened with acidulated wa- 
ter. In arranging such a pile a regular order must be 
observed. If a piece of zinc is at the bottom, it must be 
succeeded by a piece of flannel, then a piece of copper, 
then zinc again, and so on, the pile terminating on top 
by a piece of copper. 

If the ends of the pile, or wires connected with them, 
be touched with the moistened hands, a shock is at once 

What is the view now taken of the electromotive source ? What 
is the direction of the current? Describe the Voltaic pile. What 
are its effects ? 



VOLTAIC BATTERIES. 



151 



Fig. 117. 



sfcife 



received, and, on bringing the 
wires close together, a spark 
passes. 

There are several inconvenien- 
ces attending the original con- 
struction : it is liable to be over- 
set, is troublesome to put in ac- 
tion, and requires to be taken to 
pieces and thoroughly cleaned ev- 
ery time that it is used. Its max- 
imum effect lasts but a short time, 
owing to the weight of the su- 
perincumbent column pressing out 
the moisture from the lower pieces 
of cloth, and as soon as they be- 
come dry all action ceases. 

Volta used another form, which he called a crown of 
cups, Fig. 113, to avoid these difficulties. In it the 

Fig. US. 





Fig. 119. 



moist flannel is replaced by liquid contained in glass 
vessels, the copper, C, and zinc, Z, being connected by 
wires soldered to them. 

Cruickshank's battery consists of a box or trough, 
Fig. 119, three or 
four inches square 
at the ends, and a 
foot or more long. 
Grooves are made 
in the sides and bot- 
tom of this box, and 
into them pieces of zinc and copper, soldered face 
to face, are fastened water-tight by cement. These 
grooves are about half an inch apart, and into their in- 
terstices acidulated water is poured, care being taken 

What are its inconveniences? Describe the crown of cups. De- 
scribe Cruickshank's battery. 




152 daniell's battery. 

that the metals are arranged in the same direction, so 
that if the series begins with a copper plate it ends with 
a zinc. The apparatus is obviously equivalent to Vol- 
ta's pile laid on its side, and the facility for charging it, 
and removing the acid when the experiments are over, 
is very great. From the two extremities flexible cop- 
per wires pass ; they are called the polar wires, or elec- 
trodes of the battery. 

The object of amalgamating the zinc in Voltaic bat- 
teries is to prevent what is termed local action, a waste 
in which much metal is consumed, without adding to 
the power of the current, and which likewise deterio- 
rates the acid liquid by the accumulation of sulphate of 
zinc. When amalgamated, all the zinc consumed aids 
in the current. 

When it is required to have a current, the intensity 
Fig. 120. of which remains constant for a length of 
time, Daniell's battery is to be preferred. It 
consists of a copper cylinder, G r Flg. 120, in 
which a solution of acid sulphate of copper 
is poured. This solution is kept saturated 
with the salt by means of crystals of sul- 
phate of copper resting on the shelf above 
P. The interior cylinder P A is filled with 
dilute sulphuric acid, and an amalgamated 
rod of zinc, 2, dips into it. From the cop- 
per and zinc rods project, terminated by 
binding screws, with which the polar wires 
may be connected. Twenty or thirty cells 
of this description furnish a combination of great power. 
A convenient and inexpensive form of Daniell's bat- 
tery is shown in Fig. 121. The sulphate of copper is 
contained in glass jars, and the copper cup (7, Fig. 120, 
is replaced by a sheet of copper, A, bent into a cylin- 
drical form. The. shelf for the crystals is supported by 
little pieces of copper, turned in as at d d. The slip b 
serves to connect the copper with the zinc of the next 
cell. At B C the method of arranging the cells to- 
gether is seen. 

Smee's battery is also a very valuable combination. 
It consists of a plate of platinized silver, or platinized 

What is the object of amalgamating the zinc? Describe Dan- 
iell's battery. Describe Fig. 121. 




153 




platinum, S, Fig. 122, on each side of 
which are placed parallel plates of 
amalgamated zinc, Z Z. These plates 
are held tightly against a piece of wood, 
W, by means of a clamp, 5, to which, 
and also to the silver plate,, binding 
screws, for the purpose of fastening 
polar wires, are affixed. The whole is 
suspended by means of a cross-piece of 
wood in a jar containing dilute sulphu- 
ric acid. 

The object of platinizing the silver 
plate is to facilitate the extrication of 
hydrogen from it by furnishing a rough instead of a 
smooth surface. The adhesion of hydrogen to the sil- 
ver plate enfeebles the Voltaic action, owing to the tend- 
ency of the separated components of the liquid to re- 
unite. 

Smee's compound battery, represented in Fig. 123, 

Fig. 123. 





How is Smee's battery constructed ? Why is the silver plate plat- 
inized? 

G2 



154 



GROVE S BATTERY. 




Fig. 125. 



is a series of the foregoing simple circles. The figure 
shows one containing six. cells. The position of the 
platinized silver and zinc j}lates is seen at S and Z. 
Probably the most powerful of all Voltaic combina- 
tion's is Grove's nitric acid battery. It con- 
sists of two metals and two liquids, amalga- 
mated zinc and platinum, dilute sulphuric acid 
and strong nitric acid. A jar, P, Fig. 124, 
three quarters of an inch in diameter, and 
made of porous or nngiazed earthenware, is to 
be filled with strong nitric acid, N", and in it a 
slip of platinum is placed. This porous earth- 
enware cup is then set in a glass cup, A, three 
or four inches in diameter, and is surrounded 
by a cylinder of zinc, Z, one quarter of an inch 
in thickness, and of such a size that it will readi- 
ly pass between the porous cup P and the glass. 
In the glass is placed dilute sulphuric acid. 
In this manner several cups are to be provided, 
the arrangement being zinc in contact with dilute sul- 
phuric acid and plati- 
num, in contact with 
strong nitric acid,with 
a porous cup interven- 
ing between. The zinc 
cylinder of one cell 
is connected with the 
platinum of the next 
by soldering. Fig. 
125 represents a bat- 
tery of six cups arranged for action. P is the positive 
and N" the negative pole. 

Grove's battery owes its force to the decomposition 
of water by zinc. But the hydrogen is not evolved 
from the surface of the platinum as it would be in a sim- 
ple circle; it is here taken up by the nitric acid, which 
undergoes rapid deoxidation, and therefore, during the 
use of this battery, volumes of deutoxide of nitrogen 
are evolved. A battery of fifty cups gives rise to very 
striking effects, but Hxe or ten are quite sufficient to re- 
peat most of the following experiments. 

What is the most powerful of Voltaic combinations ? Describe 
Grove's battery. What is the source of power in Grove's battery ? 





DEFLAGRATION OF METALS. 155 

In Bunsen's battery cylinders of carbon are used in- 
stead of the platinum, the best variety being that ob- 
tained from gas retorts. Another modification of this 
battery is that in which bichromate of potassa is substi- 
tuted for the nitric acid, and the noxious fumes avoided. 

On separating the polar wires of such batteries from 
each other a brilliant spark passes, and if the separation 
be gradual, a flame constantly proceeds from one to the 
other, the light of which, when the wires are of copper, 
is of a beautiful green color. 

If on the surface of some quicksilver contained in a 
glass, Fig. 126, we lower a thin piece Fig,m. 

of steel or iron wire, connected with 
one of the poles of the battery, the 
mercury being kept in contact with 
the other, the steel takes fire and de- 
flagrates beautifully, emitting bright 
sparks, and the mercury is rapidly vol- 
atilized. 

When thin metal leaves are made to 
intervene between the polar wires, they are at once dis- 
sipated, the flames they emit being of different colors 
in the case of different metals. With a battery of a 
large number of cups a file may be in the same way de- 
flagrated. 

If a piece of platinum wire be made the channel of 
communication from one pole to the other, if it does 
not fuse at once, it becomes incandescent, and remains 
so as long as the instrument is m activity. 

When the polar wires are terminated by pieces of 
well-burned charcoal or gas carbon, the light which 
passes between them when they are removed from con- 
tact is one of the most brilliant that can be obtained by 
any artificial means. With powerful batteries the pieces 
of charcoal may be separated several inches apart with- 
out the light ceasing, and then it moves from one pole 
to the other in an arched form, Fig. 127. Six hundred 
cells of Bunsen's construction will give an arc nearly 

What is the peculiarity of Bunsen's battery? What occurs on 
separating the polar wires? Describe the experiment Fig. 126. 
How may metal leaves be deflagrated? What is seen on making a 
platinum wire intervene in the circuit? How is the Voltaic arc 
formed, and what are its properties? 



156 



THE VOLTAIC ARC. 




Fi o- 12T - eight inches long, when 

the points are in a verti- 
cal position with the neg- 
ative pole below. With 
one hundred pairs the 
arc is only one inch long. 
The most intense light is 
obtained when there is 
but a slight separation, 
because, the resistance being less, more electricity passes 
in a given time, and the temperature is higher. The solid 
particles of which the poles consist are continually being 
transported across the interval separating them, a cavity 
being produced in the positive pole, which is in connec- 
tion with the platinum, and a deposit upon the negative, 
which is in connection with the zinc. The flame may 
be blown out by the breath as we blow out a candle. 

This light has been utilized for illuminating purposes, 
being employed in some lighthouses, and more exten- 
sively in lecture-table experiments. But the great cost 
and practical difficulties of its aj)plication have hitherto 
prevented its general use. 

The most refractory metals, which resist the action 
of furnaces altogether, maybe fused with ease if placed 
in an excavation in the carbon connected with the pla- 
tinum, or positive pole of the battery. The negative 
pole does not attain nearly as great a heat, except when 
the secondary current of a Ruhmkorff coil is used. 

But, in a scientific point of view, by far the most in- 
teresting experiment to be made with the Voltaic bat- 
tery is the decomposition of water. Through the bot- 
tom of a glass vase or dish, at the point a 5, Fig. 128, 
two platinum wires are introduced 
water-tight: they pass into the vase 
as at a c, b d, parallel to each other 
but not touching. Over each of these 
. wires a tube is to be inserted, the 
tube e over c, and f over d; the vase 
and tubes being previously filled with 
water, acidulated slightly to improve 
its conducting power. Xow let the 

What use is made of this light? How may metals he melted by 
the Voltaic pile? Describe the decomposition of water. 



F.'q. 128. 




COMPOSITION OF WATER. 157 

wire a c be connected with the positive pole of the Vol- 
taic battery and b d with the negative, bubbles of gas 
arise in a torrent from their extremities and pass up- 
ward in the tubes, displacing the water. The quantity 
of gas thus collecting in the two tubes is unequal, and 
whenever we stop the decomposition, there will be found 
in f double the quantity which is in e. When a suffi- 
cient amount is collected, let the tube containing the 
smaller portion of gas be cautiously removed, prevent- 
ing any atmospheric air from getting into its interior 
by closing it with the finger, and then, turning the tube 
upside down, let a stick of wood, with a spark of fire on 
its extremity, be immersed in the gas. In a moment the 
wood bursts into a flame, proving that this is oxygen 
gas. Then take the other tube, and allow to pass into 
it a quantity of atmospheric air equal to the volume of 
gas it already holds ; remove the finger and apply a 
light, there is an explosion. This shows the gas to be 
hydrogen. We therefore conclude that in this experi- 
ment water has been decomposed and resolved into its 
constituent ingredients, oxygen and hydrogen ; and far- 
ther, that in water there is by volume twice as much 
hydrogen as there is oxygen gas. 



LECTURE XXXI. 

The Electro-Chemical Theory. — Theory of the De- 
composition of Water. — Decomposition of Salts. — 
Davy's Discovery of Potassium, Sodium, etc. — TJie 
Electro- Chemical Theory. — Electrolytes. — Faraday 1 s 
Law. — Specific Electricity. — Electrotyping and Gal- 
vanizing. — Comparison of Frictioncd and Voltaic 
Electricity. — The Voltameter. — Different Species of 
Battery. 

The prominent fact connected with the decomposi- 
tion of water is the total separation of the constituent 
elements on the opposite polar wires or electrodes. 
From the positive wire oxygen alone escapes, and from 

How is it proved that it is formed of oxygen and hydrogen ? What 
are the proportions of oxygen and hydrogen in water ? What is the 
prominent fact in the decomposition of water? 







Fig. 


129 






u 




1 









H 










H 


h 















. 




I 












It 



158 DECOMPOSITION OF WATER. 

the negative, hydrogen. There is no partial admixture, 
but the separation is perfect and complete. 

Though the polar wires be separated from one an- 
other by a considerable distance, the same result is uni- 
formly obtained ; and it is to be remarked that the evo- 
lution of gas takes place on the wires alone, no bubbles 
making their appearance in the intervening space. The 
principle on which this is effected may be easily under- 
stood by supposing H H and O O, Fig. 129, to repre- 
sent atoms of hydrogen and oxygen 
respectively ; each pair of them, there- 
fore, represents a particle of water. 
Now, if we slide the upper row of 
atoms upon the lower, as shown at 
h A, o o, it is obvious that a hydrogen 
atom will be set free at one extremity of the line, and 
an oxygen atom at the other; and that, as respects all the 
intermediate pairs of atoms, though they have changed 
their places, yet every atom of hydrogen is still associ- 
ated .with an atom of oxygen, constituting, therefore, a 
particle of water, and it is at the extremities of the line 
alone that the gases are set free. So in the polar de- 
composition by the pile, all the liquid intervening be- 
tween the poles is affected, decompositions and recom- 
binations successively taking place, the hydrogen atoms 
moving in one direction, the oxygen in the other, finally 
to be set free on the surface of the polar wires. 

This capital discovery of the decomposition of water 
by Voltaic electricity was originally made by Nicholson 
and Carlyle. It is by far the most satisfactory method 
of demonstrating the constitution of that liquid. After 
it was made known, any lingering doubts which still 
remained on the minds of some chemists, in relation to 
the composite nature of water, were speedily removed. 
The apparatus that they used was intended originally 
to determine the conducting power of liquids, and con- 
sisted of a tube, into which wires were fastened water- 
tight at the two ends. On passing the current, they 
found that there was an evolution of gas at one wire, 
and that the copper of which the other consisted wasted 

Do any gas bubbles appear in the intervening space ? Explain 
the non-appearance of gas except at the poles. Who first decom- 
posed water by electricity ? Describe the apparatus. 



DECOMPOSITION OF SALTS. 159 

away. If the wires are of platinum, hydrogen and oxy- 
gen collect in the tube, and may subsequently be fired 
by a spark and the decomposed water recombined. 

In the same manner that water is decomposed by the 
Voltaic battery, so also many metallic and other salts 
yield to its influence. Thus, if into a jar containing a 
solution of sulphate of copper two metallic plates be in- 
troduced parallel to each other, and one of them brought 
in connection with the negative and the other with the 
positive pole of the battery, decomposition of the salt 
takes place. The sulphate of copper is resolved into its 
constituents, sulphuric acid and the oxide of copper; 
and the latter is reduced to the condition of metallic 
copper by hydrogen simultaneously evolved with it, 
arising from the decomposition of a part of the water. 
In this manner the copper may be deposited, with a lit- 
tle care, under the form of a tough metallic mass. 

Becquerel obtained some very beautiful results by the 
aid of weak but long-continued electrical currents, illus- 
trating the probable mode of formation of mineral sub- 
stances by such currents traversing the crust of the 
earth. If we take a glass tube bent in the form of a U, 
Fig. 130, and close the bended part with a plug of plas- 
ter of Paris, putting into one of the F . ; ^ m 
branches a solution of carbonate of soda /^~ffx 
and in the other of sulphate of copper, L 1 
immersing in one of the solutions a zinc 
plate and in the other a copper, connect- 
ed together by a piece of bent wire, the 
liquids communicate together through 
the porous plug, and crystals of the dou- 
ble carbonate of copper and soda form 
on the plate immersed in the copper so- 
lution. In the same manner, other compound salts and 
mineral bodies may be produced. 

Or, if we take a jar, A, Fig. 131, and fill it with, a so- 
lution of nitrate of copper to a, and then with dilute ni- 
tric acid to B, and immerse in it a slip of copper, C D, 
presenting equal surfaces to the two liquids, an electric 
current is generated ; the copper is dissolved in the up- 

Is water the only substance that is decomposed by a Voltaic cur- 
rent ? Give an example. What were Becquerel's experiments ? 
Describe Fig. 130. Describe Fig. 131. 





160 

Fig. 131. per solution, and is deposited in crystals at D 
in the lower. 

Becquerel has shown that in the strata of 
the earth similar actions are going on ; and 
others, by connecting the surfaces of two 
contiguous lodes of metallic ore by means of 
wires attached to a galvanometer, have suc- 
ceeded in demonstrating to the eye the ex- 
istence of these feeble but continuous cur- 
rents, which are probably the cause of the 
accumulation of different metals in regular 
beds, and of their beautiful crystalline arrangement. 

As in this manner water and various saline bodies un- 
dergo decomposition by the action of the pile, it occur- 
red to Sir H. Davy that probably other substances, at 
that time supposed to be simple, might also be decom- 
posed. He accordingly subjected the alkaline and 
earthy bodies, then reputed to be elementary, to the in- 
fluence of a powerful battery, and found that his suppo- 
sition was verified. On placing a fragment of caustic 
potassa between the poles it immediately melted ; from 
the positive pole oxygen gas escaped in bubbles, and 
from the negative small metallic globules, having the 
appearance of quicksilver, emerged. These were char- 
acterized, however, by the singular quality of an intense 
affinity for oxygen, so that they w r ould take fire on be- 
ing touched by water or even ice, and were so light as 
to swim upon the surface of that liquid. 

The results of Davy's experiments proved that the al- 
kaline substances and all the earths are oxidized bodies, 
and in most instances oxides of metals. The convulsive 
spasms of a frog's legs ended in showing that the crust 
of the earth is made up of metallic oxides, besides re- 
vealing the mystery why the magnetic needle points to 
the north. 

On these principles Davy established a division of el- 
ementary bodies into electro-positive and electro-nega- 
tive substances. The former are those which, during a 
polar decomposition, go to the negative pole, and the lat- 
ter those that go to the positive. The electro-chemical 

What is the electric state of contiguous metallic lodes? What 
was Davy's great discovery? What did his experiments prove? 
What division did he make of the elements ? 



THE ELECTRO-CHEMICAL THEORY. 161 

theory assumes that all bodies have a natural appetency 
for the assumption of the positive or negative states re- 
spectively, and that all the phenomena of chemical com- 
bination are merely cases of the operation of the com- 
mon law of electrical attraction, for between particles 
in opposite states attraction ought to take place ; and 
when in a compound body, such as water, which con 7 
sists of particles of negative oxygen and positive hydro- 
gen, the poles of an active Voltaic battery are immersed, 
they will effect its decomposition, the negative oxygen 
going to the positive pole, and the positive hydrogen to 
the negative pole. 

Davy's theory thus not only accounts for the decom- 
posing agencies of the battery, but also for all common 
cases of chemical combination, referring both to the fun- 
damental law of chemical attraction. With all its sim- 
plicity, it would be easy to show that it is founded on a 
groundless assumption, and can not account for a great 
number of well-known facts. The Voltaic pile can not 
decompose all bodies indiscriminately. An electrolyte, 
for so a decomposable body is termed, must always be 
a fluid. 

It also appears that all electrolytes must have a bi- 
nary constitution, or contain one atom of each of their 
constituent ingredients. No elementary body can be 
an electrolyte. 

Faraday's law states that the same current of elec- 
tricity, when transmitted successively through various 
electrolytes, decomposes each in the proportion of their 
respective chemical equivalents. For example, if water, 
iodide of potassium, and melted chloride of lead be used, 
and if of the water there be decomposed 9 parts by 
weight, there will be 165 of iodide of potassium and 139 
of chloride of lead. These numbers represent the atom- 
ic weights of the bodies in question. The following ta- 
ble, by Daniell, of the specific electricity of various bod- 
ies is based on the statement that the proportion of elec- 
tricity which is associated with a given weight of any 
substance is inversely as its combining proportion : 

What does the electro-chemical theory assume? Can the Vol- 
taic pile decompose all substances? What is an electrolyte, and 
what must be its composition ? What is Faraday's law ? 



162 



THE ELECTROTYPE. 



Specific 


Elect 


Hatty of Bodies. 




Electro-Positives. 


Equiva- 
lent. 


Specific 
Electr'y. 


, Electro-Negatives. 


Equiva- 
lent. 


Specific 
Electr'y. 


Hydrogen 

Potassium 

Sodium 

Zinc 


1.0 
39.2 
23.3 
32.5 
31.6 
17.0 
47.2 
31.3 
28.5 


1000 
25 
43 
31 
31 
58 
21 
32 
35 


Oxygen 


8.0 

35.5 

126.0 

78.3 
18.7 
26.0 
40.0 
54.0 
75.5 


125 
27 
8 
12 
55 
38 
25 
18 
13 


Chlorine 


Iodine /. 

Bromine 


Copper 


Fluorine 


Ammonia 

Potassa 


Cyanogen 

Sulphuric Acid.. 
Nitric Acjfl ...... 

Chloric Acid 


Soda 


Lime 





Electrolytic action occupies a very important position 
in the arts. It is extensively employed as a means of 
precipitating copper, silver, gold, lead, zinc, tin, nickel, 
platinum, and other metals from solutions of their salts. 
These processes are called electrotyping or galvanizing. 
If, for example, it were required to obtain a perfect copy 
in copper of one of the faces of a medal, let a glass 
trough, N C, Fig. 132, be filled with a solution of the 
Fig. 132. sulphate of copper, and to the 

negative wire, Z, of a Smee's 
Voltaic battery, let the medal 
N be attached, all those por- 
tions except the face designed 
to be copied being varnished 
over or covered with wax, to 
protect them from contact with 
the liquid. To the positive wire, 
S, let there be attached a mass 
of copper, C. As soon as the 
battery is in action, decomposition of the sulphate takes 
place ; metallic co]Dper is precipitated on the face of the 
medal, copying it with surprising accuracy. This cop- 
per is of course withdrawn from the sulphate in the so- 
lution, but, while this is going on, sulphuric acid and 
oxygen are being evolved on the mass of copper, C. 
They therefore unite with it ; and thus, as fast as cop- 
per is precipitated on 2sT, by oxidation new quantities 
are obtained from C, and the liquid keeps up its strength 
unimpaired. In the course of a day the medal may be 
removed. It will be found incrusted with a tough red 

What is meant by the specific electricity of bodies? Describe the 
process of electrotyping. 




ELECTROTYPING. 163 

coat of copper, which may be readily split off from it. 
It is a perfect copy of the surface on which the deposition 
took place, and in turn it may be* used as a mould for 
obtaining a great number of casts. Often it is undesira- 
ble to use the original coin or medal, and in such cases 
casts must be employed. These may be made in fusible 
metal, sealing-wax, plaster, gutta-percha, and a variety 
of other substances. The surface may be caused to be- 
come a conductor by brushing it over with fine plum- 
bago or black-lead, or else by dipping it in a weak solu- 
tion of phosphorus in ether, and, when the ether has 
evaporated, immersing it in a solution of nitrate of sil- 
ver. This leaves a thin film of reduced silver on the 
surface. 

Silver-plating is accomplished from solutions of chlo- 
ride of silver in cyanide of potassium ; gilding, from 
chloride of gold in cyanide of potassium. The metals, 
as deposited, have a dead or frosted appearance, and re- 
quire to be polished or burnished. A small quantity of 
bisulphide of carbon in the bath, however, causes the 
deposit to assume the lustre of the polished metal. 

The extent to which electrotyping has come to be ap- 
plied in the arts may be appreciated from the fact that 
in the publishing establishment of Harper and Brothers 
books are now altogether printed from copper electro- 
type casts of the type and wood-cuts, the type them- 
selves being only used in printing the proof-sheets. As 
a consequence, typography is greatly improved. 

The electricity developed by frictional means, such as 
the plate machine, can produce effects similar to those 
of Voltaic combinations ; the quantity that is required 
is, however, very great. Faraday estimates that 800,000 
discharges from a Leyden battery of 3500 square inches 
of surface would be required to decompose a single grain 
of water, yet every discharge would be competent to kill 
a small animal. The difference between the two is, that 
while, in the Voltaic action, the quantity rs great, the in- 
tensity is but small, while in the electricity of the ma- 
chine the reverse is the case. 

How may casts of medals be employed? From what solution is 
silver deposited? From what solution gold? What is the appear- 
ance of the metal at first ? Of what use is electrotyping in printing ? 
What is the difference between frictional and Voltaic electricity? 



164 



DIFFERENT VOLTAIC BATTERIES. 



An instrument, the Voltameter, was invented by Far- 
aday for measuring quantities of Voltaic electricity. It 
is represented in Fig, 133. It consists of a glass jar, 



Fig. 133. 




a 5, filled with dilute sulphuric acid. From its neck a 
tube, c, conveys the disengaged gases to a graduated 
jar, d. Through the bottom of a b two wires, connect- 
ed with platinum plates, pass. By means of mercury- 
cups connection can be made with the battery to be 
measured, and the amount of the evolved gases regis- 
ters the quantity of electricity produced. 

With a given amount of metallic surface, we can pro- 
duce Altaic batteries having different qualities. Thus, 
if we take a square foot of copper and a square foot of 
zinc, and place between them a piece of wet cloth, we 
shall have a battery which can not give shocks nor ef- 
fect the decomposition of water, but which will cause a 
fine metallic wire to become white-hot or even to fuse. 
If, again, we take a square foot of copper and a square 
foot of zinc, and cut each into 144 plates an inch square, 
and arrange them with similar pieces of cloth as a Vol- 
taic pile, the instrument will give shocks and decompose 
water rapidly. From the same quantity of metal two 
different species of battery may be made, one consisting 
of a few plates of large surface, or one of a great num- 
ber of alternations of small plates. 

Of these varieties of battery, the calorimotor of Dr. 
Hare is an example of the first. It consists of a series 

Describe the Voltameter. How may a given surface- of metal pro- 
duce batteries of different qualities ? What is Hare's calorimotor ? 



ohm's theory. 165 

of zinc plates all connected together, and a series of cop- 
per also similarly connected, constituting therefore, in 
reality, a single pair of very large surface. The great 
amount of heat evolved by this apparatus is its pecu- 
liarity. 



LECTURE XXXII. 

Ohm's Theory of the Voltaic Pile. — Electromotive 
Force and Resistance. — General Law of the Force 
of the Current. — The Rheostat. — Conductivity of 
Solids and Liquids. — Magnetism. — Phenomena and 
Laios of Magnetic Induction. — Imparting of Mag- 
netism. — Electro - Magnetism. — Oersted' } s Discov- 
eries. — The Galvanometer. — Electric Rotations. — 
Electro - Magnets. — Morse's Telegraph. — Magnetism 
and Diamagnetism. 

The phenomena of the electric current are accounted 
for by the aid of an hypothesis of which the following 
is an exposition : 

Ohm's Theory op the Voltaic Pile. 

1st. By Electromotive Force, we understand the 
causes which give rise to the electric current ; this, as 
we have explained in the simple circle, is the oxidation 
of the zinc. 

2d. By Resistance, we mean the obstacles which 
the current has to encounter in the bodies through 
which it passes. 

When we affect the electric current in any portion 
of its path, either by varying the electromotive force 
or changing the resistances, we simultaneously affect it 
throughout the whole circuit, so that in a given space 
of time the same quantity of electricity passes through 
each transverse section of the circuit. 

In any Voltaic circle, simple or compound, the force 
of the current is directly proportional to the sum of all 
the electromotive forces which are in activity, and in- 
versely proportional to the sum of all the resistances ; 
that is to say, the force of any Voltaic current is equal 

What is meant by electromotive force? What is meant by re- 
sistance? In affecting one part of a current, do we affect the rest ? 



166 ohm's theory. 

to the sum of all the electromotive forces divided by- 
all the resistances. The resistance to conduction of a 
metal wire is directly as its length and inversely as its 
section ; that is to say, the longer the wire is, the great- 
er its resistance ; and the thicker it is, the less its re- 
sistance. 

If we augment or diminish in the same proportion 
the electromotive forces and the resistances of a Vol- 
taic circuit, the force of the current will remain the 
same ; if we increase the electromotive force, the force 
of the current increases ; if we increase the resistance, 
the force of the current diminishes. 

If in two Voltaic circles of equal force the same re- 
sistance be introduced, the forces of the currents may be 
enfeebled in very different proportions ; for the newly- 
introduced resistance may in one of the circles bear a 
great proportion to the resistance already existing, and 
in the other a very insignificant proportion. 

The following, therefore, is the general law which de- 
termines the force of a Voltaic circuit : 

1st. The electromotive force varies with the number 
of the elements, the nature of the metals, and of the liq- 
uids which constitute each element, but it does not in 
any manner depend on the dimensions of their parts. 

2d. The resistance of each element of a Voltaic cir- 
cuit is directly proportional to the distance between the 
plates as occupied by the liquid, the resistance of the 
liquid itself, and the length of the polar wire connecting 
the ends of the circuit ; and inversely proportional to 
the surface of the plates in contact with the liquid, and 
to the section of the connecting wire. 

3d. The force of the current is equal to the electro- 
motive force divided by the resistance. 

The instrument, Fig. 134, serves to illustrate the re- 
sistance imposed by different metals in a Voltaic cur- 
rent, and to demonstrate that heat lessens the conduct- 
ing power of a wire. It consists of a Voltaic battery, 
the terminal wires of which go to a brass stand, where 

What is the law of resistance in a wire ? How does the force of 
a current change with changes in the electromotive force and the 
resistance ? When a new resistance is introduced into two circles, 
must they be affected alike? Give the general law of the force of a 
circuit. What' does the apparatus Fig. 134 illustrate? 



RESISTANCE TO CONDUCTION. 167 

they are connected by a thin spiral of platinum wire. 
As the current passes, the platinum spiral is caused to 

Fig. 134. 



glow. One of the terminal wires is of platinum, and 
thiSj too, is raised to redness. If now that wire be grad- 
ually immersed in a vessel of water, W, so as to be re- 
duced in temperature, more electricity will pass through, 
as is shown by the fact that the platinum spiral becomes 
more and more intensely ignited, and may even be 
fused. 

Wheatstone's Rheostat is a contrivance for increasing 
the resistance in a Voltaic circuit. It consists of coils 
of fine wire arranged in lengths of hundreds of feet, and 
of which one or more can be introduced into the circuit. 
Some one combination is used as a standard, and others 
are compared with it by the aid of the deflections of 
a galvanometer, the number of feet of wire necessary 
to reduce the deflections to the same amount being 
noted. 

The following tables exhibit the conducting power 
of solids and liquids : 

What effect has heat on the passage of a current? Describe 
Wheatstone's Rheostat. 



168 



MAGNETISM. 



Silver 100 

Copper 77 

Sodium 37 

Aluminum 33 

Magnesium 25 

Calcium 22 

Potassium 21 



Lithium 19 

Iron , 14 

Palladium 12 

Platinum 10 

Strontium 7 

Mercury 1.6 

Tellurium .0008 



Saturated Solution of Sulphate of Copper , 

(diluted with an equal bulk of Water) , 

( " " twice its bulk of Water) 

( " " four times its bulk of Water) .. 

Distilled Water ! 



.6i 

.44 
.31 
.0025 



Platinum Wire 2,500,000 

Magnetism. 
Many centuries ago it was discovered that a certain 
ore of iron, which now passes under the name of the 
magnet or loadstone, possesses the remarkable quality 
of attracting pieces of iron. Subsequently it was found 
that the same power could be communicated to bars of 
steel by methods to be described hereafter. 
Fig. 135. Bars of steel so prepared pass under the name 
® of artificial magnets; when they are of small 
size they are commonly called needles. A mag- 
netic bar bent into the shape represented in 
Fig. 135 is called a horse-shoe magnet ; and sev- 
eral magnets applied together take the name of 
compound magnets, or a bundle of magnets. 
The Chinese discovered that when a magnetic 
^ needle is poised on a pivot, as at C, Fig. 136, or 
floated on water by a piece of cork, that it spontaneous- 
ly. 136. ly takes a direction north 
c . and south, and if purpose- 
S iffe n ly disturbed from that po- 
sition, it returns to it again 
after a few oscillations. 
To that end, N, which 
points toward the north, 
the name of north pole is 
given ; the other, S, is the 
south pole. 

By a needle so suspended the fundamental fact of the 

What is the relative conducting power of the metals? What are 
the properties of a magnet? What is its effect on steel? Describe 
the properties of the magnetic needle. 





MAGNETS ATTBACT IR0X. 



169 



Fig. 137. 




attraction of a magnet for iron is verified. Present a 
mass of iron to either extremity of the needle, and the 
needle instantly moves to meet it. If a bar magnet be 
brought near a nail or a mass of iron filings, the iron 
will be suspended. 

That these effects take place through glass, paper, 
and solid and liquid substances generally, may be thus 
established : A quantity of iron filings being laid on a 
pane of glass, if a magnet be approached beneath, the 
filings follow its motions ; but if a plate of iron inter- 
vene, the magnetic influence is almost wholly cut off. 

The power of a magnetic bar is not equal in all parts. 
There is a point situated near each end which seems to 
be the focus of action. To these points the names of 
poles are given, and the line joining them is called the 
axis. 

If a bar magnet be rolled in 
iron filings, they attach them- 
selves, for the most part, at 
the two poles d c?, Fig. 137 ; 
or if such a bar be placed under a sheet of pasteboard 
on the surface of which iron filings are dusted, they ar- 
range themselves in curved lines, as shown in Fig. 138, 
which are symmet- 
rically situated as 
respects the poles 
PP. 

When, instead of 
presenting to a sus- 
pended needle a 
piece of iron, we 
present to it an- 
other magnet, phe- 
nomena of repul- 
sion as well as of attraction ensue. If the north pole 
of one be presented to the north pole of the other, re- 
pulsion takes place, and the same occurs if two south 
poles are presented ; but if it be a north and south pole, 
then attraction takes place. 

What occurs on presenting a piece of iron to a needle ? Do these 
effects take place through non-conducting substances? Where are 
the foci of action in a magnet? What occurs on rolling a bar mag- 
net in iron filings ? 

ii 



Fig. 133. 




170 MAGNETISM. 

These results may be grouped together under the 
simple law, "Like poles repel, and unlike ones attract" 

There is therefore an antagonization of effect between 
opposite magnetic poles. If a key be suspended to a 
magnet by its north pole, on the approach of the south 
pole of one of equal force it drops off. 

If we examine the force of a magnet, commencing at 
either of its poles and going toward its centre, the in- 
tensity gradually declines: it ceases altogether about 
midway between the poles. This point is termed the 
point or line of magnetic indifference. 

Magnetism may be excited in both iron and steel ; in 
the former with greater rapidity, in the latter more 
slowly. The magnetism which soft iron has received it 
instantly loses on being removed from the source which 
has given it magnetism, but steel retains its virtue per- 
manently. Soft iron is therefore transiently, hard steel 
permanently magnetic. 

When a mass of iron is in contact with the pole of a 
magnet it obtains magnetism throughout its w T hole mass, 
and can in the same manner communicate a similar qual- 
ity to a second mass brought in contact with it, and this 
to a third, and so on. Thus, if from the pole of a mag- 
net a key be suspended, this will suspend a second, and 
that a third, etc., until the weight becomes too great for 
the magnet to hold. If, having two or three keys thus sus- 
pended, we take hold of the uppermost and gently slide 
away the magnet, the moment it is removed the keys all 
fall apart, showing the sudden loss of power in soft iron. 
ng. 139. -A mass of iron can receive magnetism at a dis- 
tance from the magnet itself. To this phenome- 
non the name of induction is given ; and this dis- 
tance through which this effect can take place is 
called the ?nagnetic atmosphere. The general ef- 
fect of induction may be exhibited by bringing a 
powerful magnet near a large key, as in Fig. 139, 
when it will be found that the large key will sup- 
port smaller ones ; but as soon as it is removed 

What is the law of magnetic attraction and repulsion ? What is 
the point of magnetic indifference ? What is the difference between 
the magnetism of soft iron and steel ? What results on bringing iron 
in contact with a magnet ? What is induced magnetism ? Explain 
the term magnetic atmosphere. 



MAGNETISM. 171 

from the influence of the magnet these all drop 
off. 

When magnetism is thus induced by the action of a 
given pole, that end of the disturbed body which is 
nearest to the pole has an opposite polarity, but the 
farthest end has the same polarity as the disturbing 
pole. 

The force of magnetic action varies with the distance. 
It has been proved by Coulomb and others that the in- 
tensity of magnetic action is inversely proportional to 
the squares of the distance. At twice a given distance 
it is, therefore, one fourth, at three times a ninth, etc. 

Both magnetic polarities must always simultaneously 
occur. We can never have north magnetism or south 
magnetism alone.' Thus, if we take a long magnet, N S, 
Fig, 140, and break it in two, we shall not insulate the 
north polarity in one Fig.uo, 

half and the south in sr s 

the other, but each of 1 I 

the broken magnets g , ^ g/ , 

will be perfect in it- . k c » 

self, having two poles, ' 7 * 

one fragment being N' S', and the other N" S". 

When the poles of a magnet are polished and cover- 
ed tvith smooth plates of iron, the magnet is said to be 
armed. The piece of soft iron which passes from pole 
to pole of a horse-shoe magnet is called a keeper. The 
power of a magnet is measured by the weight its poles 
are able to carry. 

There are many ways in which magnetism can be im- 
parted to needles or steel bars, as, for example, by con- 
tact, by induction, by certain movements. By the aid 
of Voltaic currents, hereafter to be described, the most 
intense magnetic power can be communicated. 

The process of magnetization by the single touch is 
that in which we place one pole of a magnet in the mid- 
dle of a steel bar and draw it toward the end ; then, 
lifting it up in the air, return it to its former position, and 
repeat the movement several times. The magnet is now 

What is the law of decrease of magnetic action ? Can we isolate 
north or south magnetism ? How is a magnet armed ? How is mag- 
netism communicated to a steel bar ? Describe the process by sin- 
gle touch. 



172 MAGNETIZATION. 

to be reversed, and in that position moved to the oppo- 
site end of the bar, lifted up in the air, replaced, and the 
movement many times repeated. The bar thus becomes 
a magnet, each end having a pole opposite to that by 
which it was touched. Or we may place two magnets 
with their opposite ends in the middle of the bar, and 
then, drawing them apart in opposite directions, the 
same result arises. A still more powerful magnetism 
may be given, if the bar to be magnetized is laid on the 
poles of two magnets, so that the contrary poles of the 
magnets and bar coincide. 

In the double touch, two bar magnets are so tied to- 
gether that their opposite poles may be maintained a 
short distance from one another. This combination is 
then placed on the middle of the bar to be magnetized 
and. drawn toward its end ; but as soon as it reaches 
that without passing over it, it is returned to the other 
end with a reverse motion and then back again ; and 
after this has been done several times, the process is 
ended by drawing the combination off sideways when 
it is at the middle of the bar. 

The magnetism of a bar is reduced by percussion, 
scratching, or filing, and by heat a steel bar may be to- 
tally demagnetized. So, too, a mass of iron, if raised 
to redness, becomes indifferent to the presence of a mag- 
netic needle, though on cooling it is as active as ever. 

Of Electeo- Magnetism. 
In 1819 it was discovered by Oersted that if a mag- 
netic needle be brought into the neighborhood of a wire 
along which an electric current is passing, the needle is 
at once disturbed from its position, and tends to set it- 
, self at right angles to the wire. If there be an electric 
current moving in the direction A B, Fig. 141, in a 
wire, and directly over the wire and parallel to it there 
be a suspended needle, as soon as the current passes the 
needle is deflected from its position, and, if the current 
be sufficiently powerful, comes at right angles to the 
wire. The direction in which the transverse motion 
takes place depends on the relative position of the nee- 

Describe magnetizing by double touch. How may magnetism be 
reduced? Describe what occurs on bringing a needle near a con- 
ducting wire. How does the position of the needle affect the result ? 



ELECTRO-MAGNETISM. 



113 



^ 



die and the wire. Thus, 1st, if the wire be above the 
needle and parallel to it, the pole Fig. ui. 

next the negative end of the bat- A 

tery moves westward ; 2d, if the 
wire be beneath the needle, it will 
move eastward ; 3d, if the wire be 
on the east side of the needle, the 
pole is elevated ; 4th, if on the 
west, it is depressed. In all these 
positions the tendency is to bring 
the needle at right angles or trans- 
verse to the wire. 

It follows, from these facts, that 
if a magnetic needle be placed in 
the interior of a rectangle of wire, 
Fig. 142, through wdiich a current 
is made to flow, all the portions of the wire conspire to 
move the needle in the m 142> 

same direction. The 
effect, therefore, be- 
comes much greater 
than in the case of a 
single continuous wire. 

On the same princi- 
ple, if, instead of a sin- 
gle turn, the wire is re- 
peatedly coiled upon itself, as at a d da, Fig. 143, so as 
to make a great many turns, Fig. 143. 

the effect upon the included 
needle, n s, is greatly in- 
creased; and when the nee- 
dle is made nearly astatic, 
that is to say, its tendency to point north nearly de- 
stroyed, by arranging it upon an axis with another nee- 
dle similar to it in all respects, but with its poles re- 
versed, as N" S, s n, Fig. 144, the directive tendency of 
the one needle neutralizing the other, but both tending 
to turn in the same direction by the current in the coil 
of wire, inasmuch as one is within the coil and the oth- 
er above it, the arrangement forms a most delicate 
means of discovering and measuring an electric current. 
It is called a galvanometer. 

What is the effect on a needle in the interior of a rectangle ? 
What is the principle of the galvanometer? 






174 



ELECTRO-MAGNETIC ROTATION. 



Fig. 144. 




As action and reaction are always equal and contrary, 
it is obvious that if a conducting 
wire be movable and the magnet 
stationary, the latter can be made 
to impress motions on the former. 
Conducting wires may be made 
to revolve around the poles of a 
magnet, or the pole of a magnet 
around a conducting wire. Thus, 
in a glass cup, Fig. 145, let a mag- 
net, n, be fixed vertically,. and the 
cup filled with mercury. By means 
of a loop, a, let a conducting wire, 5, 
be suspended, having perfect free- 
dom of motion. If an electric cur- 
rent is made to pass down this 
wire through the mercury and es- 
cape by the path c?, the wire rotates round the pole n as 
i^r. 145. long as the current passes. From this 

and similar experiments it therefore ap- 
pears that the force exerted between a 
conducting wire and a magnet is not a 
direct attractive or repulsive power, but 
one continually tending to turn the 
movable body round the stationary one, 
deflecting it continually and acting in a 
tangential' direction. Hence it is some- 
times spoken of as a tangential force. 

If round a bar of soft iron a conduct- 
ing wire, 'covered over with silk, be spi- 
rally twisted, as in Fig. 146, whenever 
an electric current is passed the iron 
becomes intensely magnetic, and loses 
its magnetism as soon as the current 
stops. A bar an inch in diameter, 
bent so as to represent a horse-shoe, 
Fig. 147, with a wire covered with 
silk for the purpose of separating its 
successive strands from each other, 




On the same principles can the wire be made to move ? Describe 
a method of showing rotation of a wire round the pole of a magnet. 
What is the nature of the force exerted between a conducting wire 
and a magnet? Describe the construction and properties of a 
straight electro-magnet. Describe the horse-shoe electro-magnet. 



THE TELEGRAPH. 



175 



may be made to give rise to very striking results. 
Professor Henry, by a modification of Fig% 14T 
the conducting wire, succeeded in im- 
parting so intense a degree of magnet- 
ism to a piece of soft iron that it could 
support more than a ton weight. If un- 
der one of these Electro-Magnets a 
dishful of small iron nails be held, the 
moment the current passes the nails are 
all attracted, and, while they are held by 
its poles, may be moulded by the hand 
in various shapes, but as soon as the cur- 
rent stops they all fall off. 

It is upon this principle of producing 
temporary magnetism by an electric cur- 
rent that Morse's electric telegraph de- 
pends. In Fig. 148, m m is an electro-magnet, with its 

Fig. 148. 





~w\ -wl_ 



poles^ upward. The wires, W W, from the distant sta- 
tion induce magnetism in it, and draw down the soft 
iron keeper, a. At the same time the clock-work, <?, is 
set going, and a strip of paper, p p, is drawn steadily 
forward in the direction of the arrows. Whenever a 
current passes', and the keeper a is depressed, the point s 
is forced upward against the moving paper. If the cur- 

"What is the construction of Morse's telegraph ? 



176 



MAGNETIC AND DIAMAGNETIC BODIES. 



Fin. 149. 



e 



rent is but momentary, a clot only is made on the pa- 
per, but if it continue, a line is formed. Morse's tele- 
graphic alphabet consists of a set of such dots and lines, 
which by varied grouping represent the various letters 
and figures. Experienced operators do not, however, 
require the paper strip, but learn to distinguish, by the 

clicking sound of the keep- 
er falling on the magnet, 
what the transmitted mes- 
sage is. 

When different sub- 
stances are suspended be- 
tween the polar termina- 
tions of a horse-shoe elec- 
tro-magnet, in the magnet- 
ic field, as it is termed, it 
is found that some arrange 
themselves from pole to 
pole — that is, axially, and 
others transversely to that 
position, equatorially. The 
former are called magnet- 
ic, and the latter diamag- 
netic bodies. In Fig. 149, 
b is a bar of bismuth, 
which, being diamagnetic, 
has arranged itself equatorially between the poles of the 
electro-magnet, N" S. It is suspended by a fibre of un- 
spun silk, <?, so as to turn freely. The following table is 
a list of magnetic and diamagnetic bodies, those at the 
beginning having the properties most strongly marked : 




Magnetic Bodies. 



Diamagnetic Bodies. 
Bismuth. Flint Glass. 

Phosphorus. Mercury. 
Antimony. Lead. 

Zinc. Wood. 

Tin. . Beef. 
. Cadmium. Bread. 

Sodium. Etc. 

The diamagnetism of gases was shown by Faraday by 

Ts the paper strip necessary? What are magnetic and diamag- 
netic bodies? Describe Fig. 149. How did Faraday show the dia- 
magnetism of gases ? 



Iron. 


Palladium. 


Nickel. 


Crown Glass. 


Cobalt. 


Platinum. 


Manganese. 


Osmium. 


Chromium. 


Oxygen. 


Cerium. 


Etc. 


Titanium. 





THE MAGNETIC FIELD. 



Ill 



Fig. 150. 




the aid of the apparatus, Fig. 150. A tube conveyed 
the gas to be examined into the 
magnetic field. Above it three 
other tubes were arranged so 
that, under ordinary circum- 
stances, the gas passed into the 
middle one ; but, when the iron 
was magnetized, if the gas were 
diamagnetic, it passed into the 
side tubes. The passage was 
shown by placing a little am- 
monia in the lower tube, and strips of paper moistened 
with hydrochloric acid in the others. 

A taper burning in the magnetic field has its flame 
spread out equatorially, and the flame may even be di- 
vided into two parts. The same body may be caused 
to become either magnetic or diamagnetic, by changing 
the medium by which it is surrounded. Magnetism 
also exerts an influence on polarized light transmitted 
through certain transparent bodies. This may be shown 
by placing them, while under examination, in the mag- 
netic field. The beam is caused to rotate to an extent 
which depends on the nature of the body and the inten- 
sity of the magnetism. 

' If a copper cylinder, Fig. 151, filled with fusible metal, 
be so arranged, mg.vs\. 

by the aid of 
the band S S, as 
to rotate rapid- 
ly in the mag- 
netic field, the 
resistance to its 
motion is so 
great that it will seem to be grasped by an invisible 
hand. On continuing the rotation for a few minutes, 
the heat developed will be sufficient to melt the con- 
tained alloy, which may be poured out upon the table. 

What is the effect on a taper in the magnetic field ? How may 
the effect of magnetism be demonstrated by polarized light? De- 
scribe the experiment, Fig. 151. 

112 







178 



PROPERTIES OF A HELIX. 



Fig. 152. 



LECTURE XXXIII. 

Electro-Dynamics. — Ampere? s Discovery. — Properties 
of a Helix. — Cause of Magnetism. — Faraday's Dis- 
covery of Magnetic Electricity. — Magnetic Machines. 
— Ruhmkorjf s Coil. — Geissler's Tubes. — Thermo- 
electricity. — Production of Electricity by Heat. — 
Thermo - Electric Piles. — MellonVs Pile and Ther- 
mometer. — Draper's Improvements in Thermo-Elec- 
tric Pairs. — Animal Electricity. — The Torpedo. 

Soon after the relation between electricity and mag- 
netism was established by Oersted, Ampere discovered 
that there are reactions between the currents them- 
selves. Two electric currents flowing in the same di- 
rection attract each other, but two electric currents 
flowing in opposite directions repel. "Like currents 
attract, unlike ones repel." 

If a conducting wire, a 5, Fig. 152, be bent in the 

form of a helix, n s, 
its ends returning 
toward its middle, 
it exhibits all the 
properties of an 
ordinary magnet- 
ized bar. As soon 
as the current 
passes, being free- 
ly suspended, it 
points north and 
south, and is at- 
U tracted and repel- 
led by the poles 
of a magnet, just as though it were a magnet itself. 
Another arrangement, called De la Rive's ring, for il- 
lustrating the same effect, is seen in Fig. 153. A small 
simple circle, consisting of a zinc, Z, and a copper plate, 
C, connected by a coil, is suspended in a vessel of acid- 
ulated water, which is floated by a cork, D, on water. 

What is the law of reaction between electric currents ? Describe 
the electro-dynamic helix. Describe De la Rive's ring. 




MAGNETO-ELECTKIC CURKENTS. 



179 




The current runs round the coil in the direction of the 
arrows, and the ar- Fig. 153. 

rangement, obeying 
the magnetic influ- 
ence of the earth, 
turns with its plane 
pointing north and 
south, just as a mag- 
netic needle would -^ 
do. If the north 
end of a magnet, 
n s, be presented to- 
ward the loop, the 
wire will be attract- 
ed, and will place it- 
self midway between the ends of the magnet ; but if 
the south end be presented, the wire will be repelled, 
the floating combination will turn half way round so as 
to reverse its direction, and will then be attracted. 

Ampere inferred from the analogy of these instru- 
ments that the magnet owes its qualities to electric cur- 
rents circulating in it in a transverse direction. The di- 
rective action of the magnetic needle or the electric he- 
lix depends on the action of electric currents circulating 
in 'the earth, due to the unequal heating of its surface 
by the rays of the sun, the earth being regarded as an 
electro-magnet, the poles of which are nearly in the line 
of the axis of rotation. The angle between the two is 
not constant, the variation of the needle from the true 
north point exhibiting slow increases and diminutions. 

We have seen that an electric current can develop 
magnetism in a bar of iron or steel — in the former tran- 
siently, in the latter permanently. Thus, if the iron bar, 
n 5, Fig. 154, be placed in the axis of a helix of copper 
wire along which a current 
is flowing, the current de- 
velops magnetism in the 
bar. It was discovered by " 
Faraday that the converse 
also holds good, and that a 



Fig. 154. 




How does it act toward a magnet? What is Ampere's theory of 
the nature of the magnet ? What is the effect of a current running 
round a bar of soft iron ? 



180 MAGNETO-ELECTRIC CURRENTS. 

magnet can give rise to an electric current. Thus, in 
Fig. 154, let the terminations, a 5, of the helix', c, be 
brought into contact, and, having placed a soft iron bar, 
n 5, within it, let the bar be made magnetic by the ap- 
proach of a strong magnet. It at once generates a cur- 
rent which runs through the helix, c ; and if at this mo- 
ment the wires a b be drawn apart, a bright spark, 
sometimes called the magnetic spark, passes. It does 
not come, however, from the magnet itself, but is due to 
the electric current induced in the helix by the disturb- 
ing action of the magnet. If between the terminations 
aba slender wire be placed, it may be made red-hot, or 
water may be decomposed, or any of the phenomena of 
a Voltaic battery may be exhibited 
by the aid of this magneto-electric 
current. 

The same results would occur 
if, instead of introducing and re- 
moving a permanent steel magnet, 
we continually change the polarity 
of a stationary soft iron bar. Thus, 
if a #, Fig. 155, be a rod of soft 
iron surrounded by a helix, and 
there be taken a semicircular steel magnet, 1ST c S, which 
can be made to revolve on a pivot at c, things being so 
arranged that its poles, N S, in their revolutions just 
pass by the ends of the bar a b, the polarity of the bar 
will be reversed every half revolution the magnet makes, 
and this reversal of polarity will generate electric cur- 
rents in the wire. 

The magneto-electric machine used for medical pur- 
poses, Fig. 156, is constructed on the principle that if 
we coil round a piece of soft iron a conducting wire, as 
often as the iron is magnetized by the permanent mag- 
net, S, a w T ave of electricity flows through the wire. 
The soft iron being rapidly rotated by the multiplying 
wheel, and the patient being brought in relation with 
the machine by the binding-screws and handles, A B, he 
experiences a succession of shocks. 

If two conducting wires be placed parallel and near 
each other, when an electrical current is passed through 

How may a magnet produce an electric current? Describe 
Fig. ]55. What is the principle of the magneto-electric machine? 




RUHMKOKFF'S COIL. 



181 



one of them a wave of electricity flows in the opposite 
direction through the other. On the first current stop- 



Fig. 156. 




ping, another wave, called the secondary current, pass- 
es through the second wire. These momentary cur- 
rents are called, from the name of their discoverer, Fara- 
dian currents. The effects are much increased by using 

Fig. 157. 





helices instead of sim- 
ple wires. Prof. Henry 
has made many inter- 
esting observations on 
secondary currents, em- 
ploying flat ribbons of 
copper instead of wires. 
Ruhmkorff's induc- 
tion coil depends on 
the high intensity of 



What are Faradian currents ? 
korff 's coil depends ? 



What is the fact on which Ruhm- 



182 ruhmkoeff's coil. 

the secondary "currents produced by magnetic induction. 
It consists of two concentric helices of copper wire, the 
inner or primary coil, A A, Fig. 157, being of thick wire 
and only two or three hundred feet long, while the out- 
er one, B B, is several thousand feet long, and of very 
thin silk-covered wire. In the axis is a bundle of soft 
iron wires, M. The primary coil is not continuous, but 
may be broken at c d, the keeper, c7, being raised when 
M becomes magnetic and the circuit interrupted. The 
making and breaking occurs several htmdred times in 
a minute, a powerful secondary current being induced 
each time in B B. A continuous stream of sparks pass- 
es between the ends of the secondary wire, ef, No. 2 
is an end view, No. 1 being a longitudinal section. 

In addition, there is attached to the primary wire a 
species of Leyden jar termed a condenser, which in- 
creases the power of the instrument. It consists of a 
band of oil-silk or paper coated on each side with tin- 
foil, the two coatings being connected with c and d. 

By this instrument sparks twenty inches long may 
be procured, and by causing these sparks to traverse 
an air-pump vacuum an auroral light will be seen. By 
placing in the air-pump receiver a tumbler of uranium 
glass, lined partly inside with tin-foil, a cascade of elec- 
tric light will flow over on the air-pump plate. 

If the discharge take place into a space more rarefied 
than the ordinary receiver, the luminous portion is ob- 
served to be stratified, or crossed by dark bands. 

Fig. 158 represents hermetically-sealed glass tubes 
into which platinum wires have been fused, and in 
which the rarefaction is progressively more perfect. 
The rarefaction is produced by filling the tubes with 
dry carbonic acid gas, and at the same time putting 
pieces of caustic potassa, P P P P, into them. The 
bands become wider and change their shape, until, when 
a perfect void is obtained, they disappear. Material 
particles seem to be necessary to the transfer of the 
current, as in the case of the Voltaic arc. By inclosing 
a variety of substances in such tubes beautiful effects 



Describe KuhmkorfTs induction coil. What length of spark may 
be obtained? How may auroral light be produced? What are 
Geissler's tubes ? 



GEISSLER 7 S TUBES. 

Fig. 15S. 



183 




of color may be obtained. These are called Geissler's 
tubes. 

THERMO-ELECTRICITY. 

If we take a bar of antimony, a, Fig. 159, and one of 
bismuth, 6, and, having soldered them end Fig. 159. 
to end at c, pass a feeble current through 
them in a direction from the antimony to 
the bismuth, the temperature of the com- 
pound bar rises, but if the current pass in 
the opposite direction, cold is produced. 
By fixing thermometers into the substance 
of the bars these facts may be verified; and 
in the latter case, when water is placed in "^ — =*- 
a depression made for it in the bar, and the reduction 
of temperature slightly aided, it may be frozen by the 
current. 

The same compound bar of bismuth and antimony, 
having its extremities connected together by a wire, 
whenever heat is applied to the junction an electric cur- 
How may an electric current produce heat and cold ? How is an 
electric current produced by the apparatus Fig. 159? 




184 



THERMO-ELECTRIC CURRENTS. 



Fig. 160. 



^B 




rent sets from the bismuth to the antimony, and when 
cold is applied, from the antimony to the bismuth. 
These important facts were discovered by Seebeck in 
1822, and the current designated thermo-electric cur- 
rents. 

If a rectangle, Fig. 160, be composed of a bar of an- 
timony, A A, and one of 
bismuth, JB J3, on apply- 
ing heat to one of the 
junctions a current will 
run around the combina- 
tion, and a magnetic nee- 
dle suspended within be 
deflected. 

For the production of 
these thermo-electric ef- 
fects two metals are not 
necessarily required. One end of a thick metallic wire 
being made red-hot, and brought in contact with the 
other, a current instantly passes from the hot to the 
cold portion, and continues to flow in diminishing quan- 
tities until the two ends have reached the same temper- 
ature. Or if a metallic ring be made red-hot iii any 
limited portion of its circumference, as long as the heat 
passes with freedom to the right hand and the left elec- 
tric development does not appear, but if we touch with 
a cold rod the hot portion, abstracting thereby a part 
of its heat, a current in an instant runs round it. 

It is not alone in metals that these thermo-electric 
currents can be induced ; other solids, and even liquids, 
may originate them. Among metals associated togeth- 
er, the relation often exhibits singular changes. Cop- 
per and iron form a very active couple until their tem- 
perature approaches 800° ; the current then stops, and 
on continuing the heat another current is developed, 
passing in the opposite direction. The same takes place 
with a pair of silver and zinc at 248°. 

Describe the thermo-electric rectangle. How can thermo-elec- 
tric effects be produced with one metal ? Describe the peculiarities 
of a copper and iron couple. 



THEKMOELECTEIC TAIRS. 185 



TIiermo-Electric Order of Metals. 



Bismuth. 
Platinum. 
Lead. 
Tin. 



Copper and Silver. 

Zinc. 

Iron. 

Antimony. 



The current proceeds, when heated together, from 
those at the end of the list toward those which precede 
them. The thermo-electric order is entirely different 
from the Voltaic order. 

Thermo-electric currents generated in pairs of metal- 
lic bars, experiencing little resistance to conduction, 
have very little tension. The thinnest stratum of wa- 
ter is a perfect non-conductor to them. 

In any thermo-electric couple the quantity of electrici- 
ty evolved depends upon the temperature. But, as was 
shown by Professor Draper (Philosophical Magazine, 
June, 1840), it is not directly proportional to it, except 
through limited ranges of temperature ; and Ave can not, 
therefore, make use of these currents for the determina- 
tion of temperatures with accuracy, on the hypothesis 
of the proportionality of the quantities of electricity to 
the quantities of heat. 

By joining a system of bars alternately together, we 
may reduplicate the effects of a single pair. As might 
have been predicted on the theory of Ohm, and as has 
been shown in the memoir just quoted experimentally, 
where the conducting resistances remain the same, the 
quantity that passes the circuit is directly proportional 
to the number of pairs. By thermo-electric batteries of 
a sufficient number of pairs of German silver and iron, 
heated intensely at one set of junctions by a coal fire, 
and kept cool at the other by water, water may be de- 
composed with rapidity, and all the effects of Voltaic 
combinations produced. There seems to be no reason 
why such combinations should not eventually displace 
all other sources of electricity, and be used for chemical, 
galvanic, and magnetic purposes. Electricity could then 
be utilized in the construction of prime movers, in warm- 
ing apparatus, and for a thousand other applications. 

What is the tension of thermo-electric currents? Why are they 
unreliable for thermometric purposes ? How is a thermo-electric 
pile or battery made ? W T hat arc the properties of such piles ? 



THE THERMO-ELECTRIC PILE. 




Melloni's thermo-electric pile, which is by far the 
most sensitive of thermometers, 
consists of a number of bars of bis- 
muth, jB, and antimony, A, with 
the alternate ends soldered togeth- 
er, as in Fig. 161. If both ends 
are heated no effect is produced ; 
but if only one, then a current is 
sent along the wire which connects 
the last bismuth at one end with 
the first antimony at the other. 
Melloni used 30 or 40 such alterna- 
tions, arranged to present a square 
or circular face. The position of the 
galvanometer is indicated at G. 
The galvanometer is seen in Fig. 162, in section and 
perspective. A B C is the coil of the multiplier, its ter- 
minal wires resting in the connecting cups, F F'. The 
coil rests on a plate, D E, which can be made to revolve 
by means of a wheel and screw connected with the but- 
ton G. An astatic combination of needles is supported 
by the frame Q M 1ST by a silk thread, V L. To pro- 
tect the instrument from currents of air, it is covered by 
a glass cylinder, F L, strengthened by brass rings, P S, 
Y Y. KT is the basis on which the cylinder rests. 
The angle of deflection of the needle is taken as the 
measure of the temperature. 

Professor Draper introduced certain improvements in 
the construction of the thermo-electric element. Let a, 

Fig. 163, be a bar of 
antimony, and b a bar 
of bismuth. Let them 
be soldered along c d, 
and at d let the tem- 
perature be raised. A 
current is immediately 
excited ; but this does 
not pass around the 
bars a 5, inasmuch as 
it finds a shorter and 
readier channel through the metals between c and d, as in- 

Describe Melloni's pile. Describe the galvanometer. 
Draper's improvements in thermo-electric pairs? 



a 



Fig.lG3. 



m 



d 



I. 




What are 



THE GALVANOMETER. 



187 



dicated by the arrows ; nor will the whole current pass 
round the bars until the temperature of the soldered sur- 




face has become uniform. An improvement on this con- 
struction is therefore such as is represented at a! b\ 
which consists of the former arrangement cut along the 
dotted lines. Here the whole current, as soon as it ex- 
ists, is forced to pass along the bars. One of the best 
forms of a thermo-electric pair is seen in the lower fig- 
ure, where the antimony, a, and bismuth, &, are united 
by a lozenge-shaped piece of copper, c. The heat is made 
to fall on c, which becomes hot and cold with prompti- 
tude, and determines a current. 

Why should the junction be small? 



THE TORPEDO. 



^K 




Animal Electricity. 
Besides the various sources of electricity to which I 
have referred, there are certain animals which possess 
the power of controlling the equilibrium of the electric 
fluid in their neighborhood at will, being accommodated 
FifJt 1{U for this purpose with a special nerv- 

^ ous apparatus. The torpedo, a fish 
living in the Mediterranean and on 
our coast, and the gymnotus elec*^ 
tricus, Avhich is found in some of 
the fresh -water streams of South 
America, have this property. The 
electric organs of the torpedo are 
shown in Fig. 164, at a a, the su- 
perficial tissues having been re- 
moved. They are composed of 
prisms, Fig. 165, presenting divid- 
(liapbragms on which nerves ramify, and are filled 
with an albuminous saline 
liquid. About 470 of these 
are found in each of the two 
organs. The dorsal surface 
of the animal is positive and 
the ventral negative. The 
nervous supply of these organs comes from a special 
lobe, the electrical lobe, IV, Fig. 166. I is the cere- 
brum ; II, optic lobes ; III, cerebellum. UTS are 
branches of the pneumogastric, and L a branch of the 
trifacial, distributed in the electric organ. 

The shock of the torpedo passes through conducting 
bodies, but not through non-conductors. A gymnotus 
which was exhibited in London was found to deflect a 
magnetic needle powerfully by its discharge. A steel 
w r ire was magnetized by it, and iodide of potassium de- 
composed. In an interrupted metallic circle a spark 
was seen, and the induced spark was also obtained by a 
coil. The current passed from the anterior to the pos- 
terior parts of the animal. Faraday, who . performed 
these experiments, calculates that the quantity of elec- 
tricity passing at each discharge of the fish was equal 

What is the torpedo, and what are its powers ? How are the elec- 
tric organs composed ? Whence do they derive their nervous sup- 
ply? Describe the phenomena shown by the gymnotus. 




ANIMAL ELECTRICITY. 



189 



to that of a Leyden battery of 3500 inches surface 
charged to the utmost, FigW. 

and this could be repeat- 
ed two or three times 
with scarcely a sensible 
interval of time. 

As the electricity which 
these animals discharge 
depends on their nervous 
action, the production of 
it is attended with a cor- 
responding nervous ex- 
haustion. Matteucci re- 
gards the prisms as piles, 
in which a secondary elec- 
tric current is generated 
by the nervous current 
sent to them. An inti- 
mate connection is thus 
established between the 
two forces. 

The same philosopher 
has also shown that in all 
living animals there is a 
current of positive elec- 
tricity from the interior 
to the exterior of every 
muscle; and by arranging a series of half muscles so 
that the interior of one 
touched the exterior of 
the next, as in Fig. 167, 
he exhibited magnetic ef- 
fects and chemical decom- 
positions. 

Fig. 168 enables us to demonstrate the effect of the 
Voltaic current on the muscles of a frog. The animal 
is prepared by dissection, so that the legs are only con- 
nected by the nerve and a part of the spinal cord. On 
plunging the terminal wires of a battery into the cups 
of water in which the feet are, the frog will leap entire- 
ly out. 

What is Matteucci's explanation of the action of the prisms ? De- 
seribe the muscle battery. 




Fig. 16T. 




190 



ELECTRICAL EXPERIMENTS. 

Fin. 168. 




In Fig. 159 the muscular contractions that are ex- 
Fig. 169. hibited by the tongue of an ox 

when a current is passed through 
it are shown. The tongue is 
drawn out, and a nail driven 
through it into the table. On 
bringing one pole of the battery 
Fig. ito. 




in connection with the tip of 
the tongue, and the other pole 
in connection with the spinal 
cord, the tongue contracts, 
and either the nail is drawn 
out or the head pulled for- 
ward. 

Fig. 170 shows the manner 
in which, when the thighs of 
a frog have been excited, they 
may be caused to produce in- 
duced contractions in the leg 
of another frog. When the two poles of a battery are 
applied to the spine joining the thighs, we observe, 
whenever the thighs contract, convulsions simultane- 
ously occur in the foot whose nerve lies across them; 

What does Fig. 168 demonstrate ? How may the contraction of 
an ox's tongue be shown ? How may induced contractions be ex- 
hibited ? 




PART II. 



LECTURE XXXIV. 

The Nomenclature. — Tlie French Nomenclature. — 
Table of Elementary Bodies. — Nomenclature for 
Compound Bodies, Acids, Bases, and Salts. — The 
Binary Hypothesis. 

Until after the discovery of oxygen gas, the nomen- 
clature of chemistry was very loose and complicated. 
The trivial names which were bestowed on various bod- 
ies had frequently little connection with their proper- 
ties ; sometimes they were derived from the name of 
the discoverer, or sometimes from the place of his resi- 
dence. Glauber salt takes its designation from the 
chemist who first brought it into notice, and Epsom salt 
from a village in England, in which it was at one time 
made. 

It is obvious that such a system of nomenclature, as 
soon as the number of compound bodies increased, 
would not only become unmanageable, but, by reason 
of the impossibility of carrying in the memory such a 
mass of unconnectedpterms, offer a very serious impedi- 
ment to the progress of the science. Lavoisier and his 
associates, about the close of the last century, con- 
structed a new nomenclature, with a view of avoiding 
these difficulties. Its principles, with some modifica- 
tions, are now universally received. The following is a 
brief exposition of it : 

^sTatural bodies may be divided into two classes, sim- 
ple and compound ; the former are also called element- 
ary. By simple or elementary bodies we mean those 
which have not as yet been decomposed. 

Among simple substances, those which have been 

What was the nature of the nomenclature used by the older 
chemists ? When was the system now in use invented ? What is 
meant by simple or elementary bodies 9 



192 THE NOMENCLATURE. 

known for a long time retain the names by which they 
are popularly distinguished ; thus, gold, iron, copper, 
etc. ; and when new bodies belonging to this class are 
discovered, they are to receive a name descriptive of 
one of their leading properties ; thus, chlorine takes its 
name from its greenish color, and iodine from its purple 
vapor. It is to be regretted that this rule has often 
been overlooked. 

Some doubt exists as to the exact number of the ele- 
mentary bodies. It may be estimated at 68, including 
metals recently discovered, the titles of which, have not 
yet been completely established. 

Of the list of elementary bodies, the metals form by 
far the larger portion, there being 55 of them ; the re- 
maining 13 are commonly spoken of as non-metallic 
substances. By some authors these are called metal- 
loids, in contradistinction to the metals, an epithet 
which, however, is very objectionable. {See opposite.) 

Compound bodies may, for the most part, be divided 
into three groups : acids, bases, and salts. By an acid 
we mean a body having a sour taste, reddening vege- 
table blue colors, and neutralizing alkalies; by a base, a 
body which restores to blue the color reddened by an 
acid, and possessing the quality of neutralizing the prop- 
erties of an acid ; by a salt, the body arising from the 
union of an acid and a base. These definitions, however, 
are to be received w T ith considerable limitation. 

The nomenclature for acid substances is best seen 
from an example. Thus, sulphui; and oxygen unite to 
form an acid : it is called sulphuric acid, the termination 
in ic being expressive of that fact. But very frequent- 
ly two substances will form more than one acid, by 
uniting in different proportions ; in this case the termin- 
ation in ous is used; thus we have 'sulphurous acid, so 
called because it contains less oxygen than sulphuric. 
The prefix a hypo" is also used, as in hyposulphur#is 
and hyposulphuric acids : it indicates acids containing 

What is the rule for naming the elements ? What is the number 
of the elementary bodies ? Of these, to what class do the greater 
number belong ? Into what groups may compound bodies be di- 
vided? What is the definition of an acid ? What is a base ? What 
is a salt ? What do the terminations ic and ous mean ? What is 
the meaning of the prefixes hypo and hyper ? 



TABLE OF SYMBOLS AND ATOMIC WEIGHTS. 193 



Table of Elementary or Simple Substances, with their 
Symbols and Atomic or Equivalent Weights. 



Non-metallic Elements. 



Symbols 



Oxygen , 

Hydrogen..., 
Nitrogen — 

Sulphur 

Phosphorus. 

Carbon 

Chlorine 

Bromine 

Iodine 

Fluorine , 

Boron , 

Silicon , 

Selenium 



Metallic Elements. 

Potassium 

Sodium 

Lithium 

Caesium 

Rubidium 

Barium 

Strontium 

Calcium.... 

Magnesium 

Aluminum 

Glucinum 

Zirconium 

Thorium 

Yttrium 

Erbium 

Terbium 

Cerium 

Lanthanum 

Didymium 

Thallium , 



O. 
H. 

N. 
S. 
P. 

c. 

CI. 
Br. 
I. 

F. 
B. 

Si. 

Se. 



K. 

Na. 

Li. 

Ca3. 

Rb. 

Ba. 

Sr. 

Ca. 

Mg. 

Al. 

G. 

Zr. 

Th. 

Y. 

Er. 

Tb. 

Ce. 

La. 

Di. 

Tl. 



1 

14 
16 
32 
6 
35.5 
78 
126 
19 
11 
22 
40 



39 

23 

7 

133 
85 
69 
44 
20 
12 
14 
7 
34 
60 
32 
? 
? 

46 
44 
48 

203 



Metallic Elements. 



Symbols. At. Wts. \ 



Indium 

Manganese .... 

Iron 

Nickel 

Cobalt 

Zinc... 

Cadmium , 

Tin 

Chromium 

Vanadium 

Tungsten , 

Columbium.... 
Niobium (?)... 

Ilmenium 

Norium 

Pelopium (?)., 
Dianium (?).., 
Molybdenum . , 

Uranium 

Titanium 

Arsenic 

Antimony 

Tellurium 

Copper 

Lead 

Bismuth 

Silver 

Mercury... 

Gold 

Palladium .... 

Platinum 

Iridium 

Rhodium 

Osmium 

Ruthenium . . . 



In. 

Mn. 
Fe. 

Ni. 
Co. 
Zn. 
Cd. 
Sn. 
Cr. 
V. 

w. 

Ta. 

Nb. 

II. 

No. 

Pe. 

Mo. 

U. 

Ti. 

As. 

Sb. 

Te. 

Cu. 

Pb. 

Bi. 

Ag. 

Hg. 

Au. 

Pd. 

Pt. 

Ir. 

Ro. 

Os. 

Ru. 



36 
28 
28 
30 
30 
32 
56 
59 
26 
68 
92 
184 



48 

60 

24 

75 

129 

64 

32 

104 

213 

108 

100 

197 

54 

99 

99 

52 

100 



less oxygen than sulphurous and sulphuric acids. The 
prefix " hyper" is used in the same way ; thus, hyper- 
chloric acid, an acid containing more oxygen than chlo- 
ric acid. 

With respect to bases, the general termination is in 
ide. If oxygen and lead unite, we have oxide of lead ; 
and in the same manner we have chlorides, bromides, 

What are the symbols for the elementary bodies ? What are their 
atomic weights? What does the termination ide signify? 



194 NOMENCLATURE FOR BASES AND SALTS. 

iodides, and fluorides. And if these elements form 
compounds in more proportions than one, Ave indicate 
their proportion by the Greek numerals, protos, deute- 
ros, tritos ; thus we have protoxides, deutoxides, tritox- 
ides ; the protoxide of lead contains one atom of oxy- 
gen and one of lead, the deutoxide of nitrogen two 
atoms of oxygen and one of nitrogen, etc. In the same 
manner the prefixes sub, sesqui, and per are used ; thus 
a suboxide contains the lowest j^roportion of oxygen, a 
peroxide the highest proportion, and a sesquioxide in- 
tervenes between a protoxide and a deutoxide, its oxy- 
gen being in the proportion of one atom and a half. 

By an alloy we mean the substance arising from the 
union of two metals ; thus copper and zinc unite to 
form brass, which is an alloy. If one of the metals is 
mercury, the compound is called an amalgam. And 
when sulphur, phosphorus, carbon, and selenium unite 
with metals, or with each other, the termination ide is 
used ; thus we have sulphides, phosphides, carbides, etc. 

With respect to the nomenclature for salts, the term- 
inations ate and ite are used to indicate acids in ic and 
ous respectively. The sulphate of potash contains sul- 
phuric acid, and the sulphite of potash sulphurous acid. 
And as we have already seen that different oxides arise 
by the union of oxygen in different proportions, and 
these bodies frequently give rise to different series of 
salts, the operation of the nomenclature may be readily 
traced ; thus the protosulphate of iron is the sulphate 
of the protoxide of iron, but the persulphate of iron is 
a sulphate of the peroxide, and the deutosulphate of 
platinum a sulphate of the deutoxide of platinum. 
When the relative quantity of the acid and base varies, 
Latin numerals are employed ; thus the bisulphate of 
potassa contains two atoms of sulphuric acid and one of 
potassa. 

Salts are said to be neutral if neither their acid nor 
base be in excess. If the acid predominates, it is an 
acid or super-salt; if the base, it is a basic, or sub-salt. 

What do the prefixes protos, deuteros, tritos, sub, sesqui, and per 
signify ? What is an alloy ? When is the termination ide em- 
ployed? What do the terminations ate and ite indicate? What is 
the nomenclature for the salts ? , What is a neutral, an acid, a basic 
salt? 



THE SYMBOLS. 195 

When a metalloid is united to another metalloid or 
metal, or when a compound radical is united to a metal 
or metalloid, the combination is called binary, from its 
consisting of two elements. The binary compounds 
formed by chlorine, bromine, iodine, and fluorine with 
the alkaline metals are called haloid salts. It has been 
suggested that the constitution of such oxacid salts as 
nitrate of silver, for example, is similar to the haloid 
salts, and that they consist of the metal united with a 
hypothetical radical, instead of an acid united with an 
oxide. This binary hypothesis would, however, involve 
a complete change in the present nomenclature. Car- 
bonate of potash, KO, C0 2 , for example, called by its 
advocates the carbonate of potassium, would be, in real- 
ity, K C0 3 , the teroxycarbide of potassium, a radical 
C0 3 , which is not carbonic acid, being united to the 
metal. The old nomenclature will be adhered to in this 
work. 



LECTURE XXXV. 

The Symbols. — Failure of the Nomenclature in the 
Case of ' Complex Compounds, — Failure in Differ- 
ence of Grouping, — Symbols for Elementary Bod- 
ies. — Expressions for several Atoms. — "Use of the 
Flus Sign. — Expressions for Grouping. 

So long as the constitution of compound bodies is 
simple there is no difficulty in applying the nomencla- 
ture, or in recognizing from the name of the compound 
the nature and proportions of its constituents. Thus, 
protoxide of hydrogen clearly indicates a body in w T hich 
one atom of oxygen is united with one of hydrogen — 
bisulphate of potassa, a body composed of two atoms of 
sulphuric acid and one of potassa; and even in more 
complicated cases, such as the sulphato-tricarbonate of 
lead, etc., the same principles will serve as a guide. 

But when compound bodies consist of a great num- 
ber of atoms, the nomenclature ceases to be of any serv- 
ice. Thus starch is composed of twelve atoms of car- 

What is a binary compound? What is a haloid salt? What is 
the binary hypothesis ? When does the nomenclature apply ? 
When does it fail ? 



196 NECESSITY FOR SYMBOLS. 

bon, ten of hydrogen, and ten of oxygen. Fibrin is 
composed of 216 atoms of carbon, 169 of hydrogen, 68 
of oxygen, 27 of nitrogen, 2 of sulphur, and a trace of 
phosphorus. On the principles of the nomenclature, it 
would be difficult to give to the first a technical name, 
and in the case of the latter impossible. 

The peculiarity of organic compounds is, that they 
contain but few of the elementary bodies, being chiefly 
made up of carbon, hydrogen, oxygen, and nitrogen ; 
but these, as in the case of fibrin, unite in a very com- 
plicated way, very often hundreds of atoms being in- 
volved. The nomenclature is therefore inapplicable to 
organic chemistry. (See Lecture LXVIIL) 

There is also another very serious difficulty in its way. 
It has been discovered that compounds may consist of 
the same elements, united in precisely the same propor- 
tions, so that when they are analyzed they yield pre- 
cisely the same results, and yet they may, in reality, be 
very different substances. Identity in composition is 
no proof of the sameness of bodies. Thus we may have 
the same elements uniting together in the same 'propor- 
tion, and yielding a solid, a liquid, or a gas indifferently. 
This result may depend on several causes, as will be 
presently explained ; but among these causes I may 
here specify what is termed by chemists " Grouping." 
Thus, suppose four elementary bodies, ABC D, 'unite 
together, there is obviously a series of compounds which 
may arise by permuting or grouping them differently, 
as in the following example : 

(1) A + B + C + D. 

(2) AC + B D. 

(3) AD + C B. 
etc. etc. 

The method of symbols which is designed to meet 
these difficulties, and is, in reality, an appendix and im- 
provement upon the nomenclature, was originally intro- 
duced by Berzelius ; but the form which is now most 
commonly adopted is that of Liebig and Poggendorff. 
The advantages which have been found to accrue from 

What is the peculiarity of organic compounds ? Why is the nom- 
enclature inapplicable ? Is identity of composition any proof of the 
identity of bodies ? What is meant by grouping ? Give an exam- 
ple. 



CONSTRUCTION OF SYMBOLS. 197 

it are so great, that it is now introduced into every part 
of chemistry, so that it is impossible to read a modern 
work on this science without having previously master- 
ed the symbols. 

The student should not be discouraged at the mathe- 
matical appearance of chemical formulae. He will find, 
by a little attention, that they are founded upon the 
simplest principles, and involve merely the arithmetical 
operations of addition and multiplication. The follow- 
ing is a brief exposition of their nature : 

For the symbol of an elementary substance we take 
the first letter of its Latin name, as is shown in the ta- 
ble given in the last lecture. Those symbols should be 
committed to memory. But as it happens that several 
substances sometimes have the same initial letter, to dis- 
tinguish between them we add a second small letter. 
Thus carbon has for its symbol G; chlorine, Gl. / cop- 
per (cuprum), Cu.; cadmium, Gd n etc. It may be ob- 
served that in the case of recent Latin names the Ger- 
man synonym is always used ; thus potassium is called 
kalium in Germany, and has for its symbol K. / sodium 
is called natrium, and has for its symbol JVa.^ etc. 

But a symbolic letter standing alone not merely rep- 
resents a substance ; it farther represents one atom of 
it ; thus G means one atom of carbon, and one atom 
of oxygen. 

If we wish to indicate that more than one atom is 
present, we affix an appropriate figure, as in the follow- 
ing examples: G 12 'JEf l0 .O l0 . Thus nitric acid is com- 
posed of one atom of nitrogen united to five of oxygen, 
and we write it N0 5 . 

When a compound, formed of several compounds, is 
to be, represented, we make use of an intervening com- 
ma ; thus strong oil of vitriol is composed of one atom 
of sulphur and three of oxygen, united with one atom 
of water, which is composed of one atom of oxygen and 
one of hydrogen, and we write it $0 3 , HO. 

If we desire to indicate that compounds are united 
with a feeble affinity, we make use of the sign -f ; thus 

What are the symbols for elementary bodies? When is a second 
letter necessary? What does a single symbol standing alone repre- 
sent? How are more atoms than one represented? How is the 
comma employed ? What is the use of the plus sign ? 



198 WRITING OF SYMBOLS. 

the composition of sulphuric acid may be written S0 3 , 
or S0 2 + O y the latter formula implying that one of the 
atoms of oxygen is held by a feebler affinity than the 
other two. 

When a large figure, or coefficient, is placed on the 
same line as the symbol, and to the left of it, it multi- 
plies that symbol as far as the first comma or + sign ; 
or, if the formula be placed in a parenthesis, it multiplies 
every letter under the parenthesis; thus 2S0 3 , IlO, 
HO or 2$0 3 -f-HO+HO mean two atoms of sulphuric 
acid united with one of potassa and one of water, form- 
ing the bisulphate of potassa;. but 2(#0 3 , KO, HO) 
would represent two atoms of a salt composed of one 
of sulphuric acid, one of potassa, and. one of water, the 
figure here multiplying all under the parenthesis. 

The advantages which arise from the use of these 
simple rules are very great ; we can, even with the most 
complex bodies, not only express their composition, but 
also the molecular arrangement or grouping of their at- 
oms; we can follow them through the most intricate 
changes, and without difficulty trace out their meta- 
morphoses. For example, analysis shows that alcohol 
is composed of (7 4 , H& 2 ; 

but many facts in its history lead us to know that its 
molecular constitution is 

(O t H s )0+ffO; 
that is to say, it contains a compound radical, CJEE& to 
which the name of ethyle has been given, and this fact 
being understood, we see at once that upon the princi- 
ples of the nomenclature the true name for alcohol is the 
hydrated oxide of ethyle; moreover, alcohol is derived 
by processes of fermentation from sugar. The constitu- 
tion of dry fruit sugar is 

^12> -H-Yto yn* 

This complex atom, under the influence of active yeast, 
is split into 

2(0,11,0,)..... 4(C0 2 ), 
that is to say, into two atoms of alcohol and four of 
carbonic acid gas ; and, accordingly, we find, during fer- 
mentation, that the sugar disappears, alcohol forming in 
the liquid, and carbonic acid gas escapes. 

How far does a coefficient multiply? What are the advantages 
arising from the symbols? Give an example in the case of alcohol. 



LAWS OP COMBINATION. 199 

The student should accustom himself to the transla- 
tion of the nomenclature into symbols, and symbols into 
the nomenclature, in cases where it is possible, for it is 
absolutely essential that he should be perfectly familiar 
with the process. 



LECTURE XXXVI. 

The Laws of Combination. — Law of Fixed Propor- 
tions, — Numerical Law. — Multiple Law. — Modes of 
expressing Composition. — Proportions, Equivalents, 
and Atomic Weights. — Relation between Combining 
Volumes and Atomic Weights. — Table of Specific 
Gravities and Atomic Weights. — Gerhardfs System 
of Notation. 

It has been shown in the first lectures that material 
substances possess an atomic constitution, and all the 
phenomena of chemistry bear out this conclusion. It 
follows, therefore, when substances combine with each 
other and give rise to new products, the union takes 
place by the atoms of the one associating themselves 
with the atoms of the other ; and as these atoms pos- 
sess weight and other properties which are specific, 
there are certain circumstances, easily foreseen, which 
must attend such combinations. 

1st. The constitution of a compound body must al- 
ways be fixed and invariable. This arises from the fact 
of the unchangeability of the properties of atoms ; one 
atom of water will always be composed of one atom of 
oxygen and one of hydrogen; one atom of carbonate of 
lime will always consist of one atom of carbonic acid 
and one of lime. Or, more generally, if a good analysis 
of water has shown that nine grains of that substance 
contain eight grains of oxygen and one of hydrogen, ev- 
ery subsequent analysis will correspond therewith. 

2d. The proportions in which bodies are disposed to 
unite with each other can always be represented by cer- 
tain numbers ; these numbers being, in fact, the relative 

In what manner does combination of bodies take place? What 
is meant by the law of fixed proportions ? What by the numerical 
law? 



200 LAWS OF COMBINATION. 

• 

weights of their atoms. Thus water is composed of an 
atom of oxygen and one of hydrogen ; and inasmuch as 
the oxygen atom is eight times heavier than that of hy- 
drogen, it necessarily follows that in every nine parts of 
water we shall have eight of oxygen and one of hydro- 
gen. These numbers are, therefore, spoken of as the 
combining proportion or equivalents of the substances 
to which they are attached. If, farther, we examine, 
when oxygen and sulphur unite, what are the relative 
quantities, we shall find that eight parts of oxygen com- 
bine with sixteen of sulphur, forming hyposulphurous 
acid. And if sulphur and hydrogen unite, it will be 
found that sixteen of sulphur combine with one of hy- 
drogen. In this manner, by examining the various ele- 
mentary bodies, we find that certain numbers are ex- 
pressive of the proportions in which they are disposed 
to unite, and these numbers represent the relative weight 
of their atoms ; thus, if 1 be taken as the atomic weight 
of hydrogen, that of oxygen is 8, that of sulphur 16, etc. ; 
the atomic weights of the elementary bodies have been 
given in Lecture XXXIV. 

3d. If two substances unite with each other in more 
proportions than one, those proportions bear a very sim- 
ple arithmetical relation to one another; thus 14 grains 
of nitrogen will successively unite with 8, 16, 24, 32, 40 
grains of oxygen, forming successively the protoxide of 
nitrogen, the deutoxide, hyponitrous acid, nitrous acid, 
and nitric acid. And when the numbers expressing the 
amount of oxygen are examined, it is seen that they are 
in the second twice, in the third thrice, in the fourth four 
times, and in the fifth five times the amount of the first ; 
they are, therefore, simple multiples of it. The reason 
of this is plain when we write the constitution of these 
bodies in symbols ; they are successively, 

no . . no 2 . . jsto 3 . .&o A . . jsto 5 i 

and if one atom of oxygen weighs 8, two must weigh 
16, three 24, four 32, etc.; the multiple law, therefore, 
is a necessary consequence of the combination of atoms. 
Observation has shown that there are two series ac- 
cording to which bodies may unite with each other : 

Give an example in each case. What do the numbers represent? 
Give examples of these numbers. What is meant by the multiple 
law ? Give an example of it in the case of nitrogen and oxygen. 



LAWS OF COMBINATION. 201 

(1.) 1 atom of A may unite with 1, 2, 3, 4, 5, etc., atoms of B. 
(2.) 1 atom of A may unite with J, 1, 1J, 2, 2 J, 3, etc., atoms of B. 

But as an atom is indivisible, there can be no such 
thing as a half atom; consequently the second series be- 
comes, 

(3.) 2 atoms of A may unite with 1, 2, 3, 4, 5, etc., atoms of B. 

The three foregoing laws are known under the name 
of the laws of combination ; they are the law of definite 
proportions, the law of numbers, and the multiple law. 

.There are three ways in which the composition of a 
substance may frequently be expressed: 1, by atom; 
2, by weight ; 3, by volume. Thus the constitution of 
water, by atom, is one of oxygen to one of hydrogen; 
by weight, it is one of hydrogen to eight of oxygen ; 
and by volume, two of hydrogen to one of oxygen. 
These different modes of expression involve nothing 
contradictory; they are all reconciled by the statement 
that the atom of oxygen is eight times as heavy as that 
of hydrogen, but only half the size. 

By some authors the terms combining proportion and 
equivalent are used ; they are to be understood as hav- 
ing the same signification as atomic weight. And as 
we know nothing of the absolute weight of atoms, but 
only their relative proportions to each other, we may 
select any substance with which to compare all the rest, 
and make it our unit 'or term of comparison. In this 
book hydrogen is employed for this purpose, and its 
atomic weight is marked 1 ; on the Continent of Eu- 
rope oxygen is selected, and marked 100. It is obvious 
that this does not affect the relationship of the num- 
bers, for it is the same thing whether we state the atom- 
ic weights of hydrogen and oxygen as 1 to 8, or as 12£ 
to 100. 

Combinations may take place in two different ways : 
1st, in definite proportions ; 2d, in indefinite proportions. 
It is to the former that all the foregoing observations 
and laws apply. One grain of hydrogen will not unite 

What are the two series in which bodies may unite? In what 
ways may the composition of a body be expressed ? How is the con- 
tradiction reconciled ? What do proportion and equivalent signify ? 
What substances are used as standards of comparison ? What are 
the two modes of combination ? 

T2 



202 COMBINING VOLUME AND ATOMIC WEIGHT. 

with nine or seven grains of oxygen, but only with 
eight. But one drop of spirits of wine may combine 
with one of water, or with a pint, or a quart, or ten 
gallons. This is what is understood by union in indefi- 
nite proportions. 

When two gaseous bodies unite, their combining pro- 
portions bear a simple relation to each other ; one vol- 
ume of hydrogen unites with one of chlorine, and pro- 
duces two volumes of hydrochloric acid. And in the 
case of the five compounds of nitrogen just referred to, 
two volumes of that gas combine successively with 1-, 2, 
3, 4, 5 of oxygen. 

A relation, therefore, exists between the combining 
volume and the atomic weight of gaseous bodies. If 
the weight of a given volume of oxygen be called 1000, 
that of an equal volume of hydrogen will be 62.5, these 
numbers representing, of course, the specific gravity of 
the two gases. The proportion in which they unite is 
one volume of oxygen to two of hydrogen to form wa- 
ter; the relative weights of these quantities, therefore, 
would be 100.0 to 6.25 x2 ; that is, 100.0 to 12.50; but 
these numbers are the atomic weights of the bodies re- 
spectively. From such considerations, it was at one 
time supposed that, in the case of all gases, the specific 
gravities would correspond to the atomic weights. Ex- 
perience has, however, shown that this is not the case, 
as is seen in the folio win % table : 



Gas or Vapor. 



Specific Gravities. 



Hydrogen = l 



Chemical Equivalents. 



By Volume. 



By Weight 



Hydrogen 

Nitrogen , 

Carbon (hypothetical)., 

Chlorine 

Iodine 

Bromine 

Mercury 

Oxygen 

Phosphorus 

Arsenic 

Sulphur 



.0690 

.9727 

.4213 

2.4700 

8.7011 

5.3930 

6.9690 

1.1025 

4.3273 

10.3620 

6.6480 



1 
14.12 
6.12 

35.84 
126.30 

78.40 
101 

16 

62.8 
150.8 

96.48 



100 
100 
100 
100 
100 
100 
200 

50 

25 

25 

16.66 



1 
14.15 

6.12 

35.42 

126.30 

78.40 

202 

8 
15.70 
37.7 
16.10 



From this it is seen that if the combining volume of 
hydrogen, nitrogen, or chlorine be taken as unity, that 

What relation is observed when gases combine by volume ? What 
is the relation between specific gravities and atomic weights ? 



€rERHAKDT 7 S SYSTEM. 



203 



of oxygen is one half, of vapor of phosphorus one fourth, 
and of vapor of sulphur one sixth. 

A new system of notation has been proposed by Ger- 
hardt, with a view to establish a constant relation be- 
tween the atomic weight of bodies, their specific gravi- 
ties, and vapor volumes. He suggests that hydrogen 
should be the standard unit for the atomic weight, com- 
bining volume and specific gravity, and that the equiva- 
lents of certain bodies should be doubled, as follows: 



Hydrogen., 

Oxygen 

Sulphur ..., 
Selenium.., 
Tellurium . , 
Carbon 



Symbol?. 



At. Wts. 



H. 


i 


0. 


16 


&. 


32 


Se. 


79 


Te. 


128 


a 


12 



The symbols that are italicized represent the doubled 
atomic weights. 

The specific gravity is referred by Gerhardt to hydro- 
gen instead of air, and this has the advantage of gen- 
erally representing by one set of figures both specific 
gravities and atomic weights. Thus oxygen is 16 times 
heavier than hydrogen ; its specific gravity would there- 
fore be 16; and as it combines with hydrogen in the 
proportion of 8 to 1, that is, as 16 to 2, it will take 2 at- 
oms of hydrogen to form water. Hydrogen is thus sup- 
posed to unite in the proportion of two atoms to one of 
oxygen, and hence water is a suboxide of hydrogen, 
H 2 0. Nitric acid becomes NO^H, and sulphuric acid 
SO A H 2 . 

The radical change that this system requires in the 
nomenclature, together with the straining of facts that 
it demands, have prevented its general adoption. 

On the principles which have just been developed, we 
can often calculate the specific gravity of a compound 
gas with more accuracy than it can be determined ex- 
perimentally. Thus hydrochloric acid, which consists 
of equal volumes of chlorine and hydrogen united, with- 

What is the object of Gerhardt's nomenclature ? What sugges- 
tions does he make? What is the advantage of referring specific 
gravities to hydrogen ? On this theory, what is the composition of 
water ? How may the specific gravity of a compound gas be de- 
termined ? 



204 CALCULATION OF SPECIFIC GKAYITY. 

out condensation, must have a specific gravity of 1.2695, 
because the specific gravity of hydrogen being 0.0690, 
and that of chlorine 2.4700, the sum of which, 2.5390, is 
the weight of two volumes of hydrochloric acid, and, 
therefore, if we divide by 2, the quotient, 1.2695, is equal 
to the weight of one volume ; or, in other words, the 
specific gravity of the compound gas. 

Sometimes, also, we can determine the specific gravi- 
ty of a vapor by calculation when it is impossible to do 
so experimentally. Assuming that one volume of car- 
bonic acid gas contains one volume of oxygen and one 
of carbon vapor, we have, 

Specific Gravity of Carbonic Acid 1. 5238 

" " Oxygen 1.1025 

" " Carbon Vapor 4213 

The hypothetical specific gravity of the vapor of carbon 
is therefore .4213. 

The rule for the calculation of specific gravities, on 
the foregoing principles, is, "Multiply the specific grav- 
ities of the simple gases or vapors respectively by the 
volumes in which they combine ; add those products to- 
gether, and divide the sum by the number of volumes 
of the compound gas produced." 



LECTURE XXXVII. 

Constitution of Bodies. — Crystallization, — Systems 
of Crystals. — Dimorphism. — Isomorphism. — Iso- 
morphous Groups. — Isomerism. — Metameric and 
Polymeric Bodies. — Allotropic States of Bodies. 

It frequently happens that substances assuming the 
solid form from the liquid or vaporous states, take on 
a geometrical figure, being terminated by sharp edges 
and solid angles; under such circumstances, they are 
said to crystallize. Thus common salt will crystallize 
in cubes, and nitrate of potassa in six-sided prisms. 

The various geometrical forms which crystals can 

How is the hypothetical specific gravity of the vapor of carbon 
determined ? Give the rule for calculating specific gravities of com- 
pound gases. 



SYSTEMS OF CRYSTALLIZATION. 



205 



thus assume may be divided into six classes or sys- 
tems: 

(1.) The Regular system. 

(2.) The Rhomhohedral system. 

(3.) The Square Prismatic system. 

(4.) The Right Prismatic system. 

(5.) The Oblique Prismatic system. 

(6.) The Doubly Oblique Prismatic system. 

This division is founded on the relations of certain 
lines or axes which may be supposed to be drawn 
through the centre of the crystal round which its parts 
are symmetrically arranged. 

THE REGULAR SYSTEM. 

This has three equal axes at right angles to each 
other. 

The letters a a show the direction of the axes. The 
figure {Fig. 171) represents: 1. The cube; 2. Regular 

Fig. 171. 




octahedron ; and, 3. Rhombic dodecahedron. 

THE SQUARE PRISMATIC SYSTEM. 

This has three axes, two of which are equal and the 
third of a different length. 

Fig. 172. 



>-• 



H. 



< K')> > 



&=& 



"a"\7 




What are the six systems of crystallization? Upon what is this 
division founded? In the regular system, what is the relation of 
the axes? In the square prismatic system, what is their relation? 



206 



SYSTEMS OF CRYSTALLIZATION. 



a a is the principal axis, b b the secondary one. In 
the figure {Fig. 172), 1 is a right square prism, with the 
axes on the center of the sides, b b; 2 is a right square 
prism, with the axes in the edges ; 3 and 4, correspond- 
ing right square octahedrons. 

THE EIGHT PRISMATIC SYSTEM 

has three axes, a a,b b,c c, of unequal lengths, at right 
angles to each other. 

In the figure {Fig. 173), 1 is a right rectangular 

Fig. 1T3. 



'<l 



'•e~~ {*•&> 




prism; 2. Right rhombic prism ; 3. Might rectangular- 
based octahedron ; 4. Right rhombic-based octahedron. 

THE OBLIQUE PRISMATIC SYSTEM 

has three axes, which may be unequal ; two are placed 
at right angles to each other, and the third is oblique 
to one and perpendicular to the other. 

In the figure {Fig. 174), 1 is an oblique rectangular 

Fig. 174 




prism; 2. Oblique rhombic prism ; 3. Oblique rectan- 
gular-based octahedron ; 4. Oblique rhombic-based octa- 
hedron. 

What is the relation of the axes in the right prismatic system ? 
In the oblique prismatic, what is it ? 



SYSTEMS OF CRYSTALLIZATION. 



207 



THE DOUBLY OBLIQUE PRISMATIC SYSTEM 

has three axes, which may be all unequal and all oblique. 
In the figure {Fig* 175), 1 and 2 are doubly oblique 

Fig. 175. 

a 




prisms, and 3 and 4 doubly oblique octahedrons. 

THE RHOMBOHEDRAL SYSTEM 

has four axes, three of which are equal in the same 
plane, and inclined at angles of 60° ; the fourth, which 
is the principal axis, is perpendicular to all. 

In the figure {Fig. 176), 1 is the regular six-sided 



Fig. 176. 



<vjJLJX 




prism; 2. the dodecahedron; 3. Mhombohedron ; 4. 
another dodecahedron. 

It often happens, owing to a change in the deposit of 
new matter on a crystal while forming, that other fig- 
ures than the proper one is produced; thus the cube 
may pass into the octahedron, as shown in Fig. 177. 

The effect may perhaps be better conceived by im- 
agining the solid angle of the cube 1 to be cut off by 
planes equally inclined to the constituent faces ; 2 rep- 

What is the relation in the doubly oblique prismatic ? How many 
axes are there in the rhombohedral system, and what is their rela- 
tion ? In what manner may crystals of one form pass into another, 
as the cube into the octahedron ? 



208 



THE GONIOMETER. 

Fig. ITT. 

3/ 




resents an increased removal of the same kind ; 3, one 
still farther advanced. 

Sometimes it happens that each alternate plane of a 
crystal grows at the expense of the adjacent one, giving 
rise to hemihedral) or half-sided crystals, as is shown in 
Mg.ll8, which represents the tetrahedron, arising in 

Fig. ITS. 
1 /I \ 2//~ 




this manner from the octahedron by the growth of each 
alternate face. 1. The octahedron partially modified ; 
2. The change farther advanced; 3. The tetrahedron 
completed. 

The angles of crystals are measured by goniometers, 
Fig. 1T9. of which there are sever- 

al kinds ; as the common 
goniometer, and Wollas- 
ton's reflecting goniome- 
ter. This instrument is 
represented in Fig. 179. 
The crystal to be meas- 
ured, f, is fixed upon a 
movable support, c?, which 
is in connection with the 
button-headed axis of the 
goniometer, o, which pass- 
es through a larger axis 
in the upright, b ; a is a 
divided circle, and e its vernier, which is fixed immova- 
bly on the upright, 6. 

The edge of the crystal, which is formed by the two 

What are hemihedral crystals, and how are they produced ? De- 
scribe the reflecting goniometer. 




DIMORPHISM. 209 

faces whose inclination is to be measured, is to be set 
parallel to the axis of the instrument ; and having, by 
means of the button, o, turned the crystal until some 
definite object, such as the bar of a window, is seen dis- 
tinctly reflected from it, the larger milled head is turned, 
and with it the divided circle and crystal, until the 
same object is again seen by reflection from the second 
face. The angle through which the great circle has 
moved, subtracted from 180°, gives the angle included 
between the two crystalline faces, or their inclination 
to each other. 

As a general rule, the same substance, crystallizing 
under the same circumstances, will produce crystals be- 
longing to the same system. Cases, however, are known 
in which the same substance belongs to different sys- 
tems. Thus sulphur will crystallize in rhombic prisms, 
and also rhombic octahedrons. By dimorphous bodies 
we therefore mean substances which will afford crystals 
belonging to two different systems. 

Dimorphism is frequently connected with the tem- 
perature at which the crystals were produced. Thus 
carbonate of lime, at ordinary temperatures, yields 
rhombohedrons, but at the boiling point of water right 
rhombic prisms; and with this difference of form a dif- 
ference of chemical qualities may occur ; the deutosul- 
phide of iron, for example, crystallizes in cubes which 
remain unacted upon by water or air ; but in the right 
rhombic form it undergoes rapid oxydation in moist 
air, producing sulphate of iron. Commonly one of the 
forms of a dimorphous body is less stable than the other, 
and if the transition takes place abruptly, it is some- 
times attended by a flash of light. 

It was discovered by Mitscherlich that when different 
compound bodies assume, the same form, we are often 
able to trace a remarkable analogy in their chemical 
composition. Thus the chloride of sodium, the iodide 
of potassium, the fluoride of calcium, etc., crystallize in 
the first system. These substances are all constituted 

How is the goniometer used? What is meant by dimorphous 
bodies? What effect nas temperature on the formation of crystals? 
What connection is there between chemical qualities and dimorph- 
ism? What relation is there in the form and composition of iodide 
of potassium and chloride of sodium? 



210 ISOMORPHISM. 

* 

upon a common type, in which we have one atom of a 
metal united to one atom of an electro-negative radical; 
or, taking M as the general symbol for the metals, and 
H for the electro-negative radicals, the class is consti- 
tuted upon the type 

M, i?, 

and thererefore includes such bodies as 

KCl..lSraCl..KBr..KF..CaF. t AmCl...,ztc. 

Such substances are called isomorphous bodies, and the 
designations isomorphous elements, isomorphous groups 
are used, being derived from urog, equal, jioptyr}, form. 

Let us take a second more complicated case. The 
formula for common alum, the sulphate of alumina and 
potash, is, 

KO, S0 3 +Al 2 3 , SS0 3 +2±HO 
Ammonia alum is AmO, S0 3 +A! 2 3 , SS0 3 +2±HO 
Chrome alum is KO, S0 3 +Cr 2 3 , 3£0 3 +24i20 
Iron alum is KO, S0 3 +Fe 2 3 , 3S0 3 +24:HO 

And in the same way an extensive family of alums may 
be formed by the substitution of a limited number of 
various other bodies comprised in the general formula, 

mO, $0 3 , + M 2 3 , SS0 3 +24,JST0, 

in which m represents any metal belonging to the po- 
tassium group, and M any one belonging to the alumi- 
num group. 

All these alums crystallize with the same form, and 
such illustrations afford us reason to believe that that 
similarity of form is due, in a great measure, to the 
grouping ox arrangement of the constituent atoms; that 
in a compound molecule the substances which can re- 
place one another without giving rise to a change of 
external form must have certain relationships to each 
other. We call them, therefore, isomorphous. 

From the external forms of bodies we may next turn 
to their internal constitutions, calling to mind w r hat has 
been already observed in Lecture XXXV., that identi- 
ty of composition by no means implies identity of char- 
acter. Two substances may be composed of the same 

Why are they called isomorphous bodies? Give an example of 
isomorphism in the case of the alums. What general conclusion 
may be drawn from these facts ? 



METAMERIC AND POLYMERIC BODIES. 211 

elements, united in the same proportions, and yet be to- 
tally unlike; and it is obvious that this may be due to 
two different causes: 1st. Difference of grouping; 2d. 
Difference in the absolute number of atoms. 

Difference of grouping I have already explained in 
the lecture just quoted ; and with respect to difference 
in the absolute number of atoms, the effect is obvious 
from an example. Thus we have as the constitution of 

Aldehyde CJI±0 2 

Acetic Ether C^HqO^ 

And these bodies, if analyzed, would, of course, yield 
precisely the same proportions in 100 parts, the true 
difference being that the atom of acetic ether contains 
twice as many constituent atoms as that of aldehyde, 
and is, therefore, exactly twice as heavy, though equal 
weights of the two will yield equal quantities of their 
constituents. 

To these peculiarities the term isomerism is applied, 
and by isomeric bodies we mean bodies composed of 
the same elements in the same proportion, but differing 
in properties. When isomerism arises from difference 
in grouping, the bodies are said to be metameric ; and 
when it arises from difference in the absolute number 
of atoms, they are called polymeric. 

There is a third cause which gives rise to the phe- 
nomena of isomerism : it is the allotropic condition of 
elementary bodies. Carbon, for example, exists under 
a number of different forms ; we find it as charcoal, 
plumbago, and diamond. They differ in specific gravi- 
ty, in specific heat, and in their conducting power as 
respects caloric and electricity. In their relations to 
light, the first perfectly absorbs it, the second reflects it 
like a metal, the third transmits it like glass. In their 
relation to oxygen they also differ surprisingly; there 
are varieties of charcoal that spontaneously take fire in 
the air, but the diamond can only be burned in pure 

What two causes may give to bodies of the same composition dif- 
ferent characters ? Give an example of the effect of difference of 
the absolute number of atoms. What is meant by isomerism? What 
are metameric and polymeric bodies? What is meant by the allo- 
tropic condition of bodies ? What allotropic states does carbon pre- 
sent? 



212 ALL0TR0PIS3I. 

oxygen gas. The second and third varieties do not be- 
long to the same crystalline form. 

It is now known that a great many elementary sub- 
stances are affected in this manner. Professor Draper 
showed that this is the case with chlorine gas, which 
changes under the influence of the indigo rays (Philo- 
sophical Magazine, July, 1844). In the same manner it 
has been long known that iron exists in two states : 
1st. In its ordinary oxidizable state ; 2d. In a condition 
in which it simulates the properties of platinum or gold. 

There can be no doubt that these peculiarities are 
carried by these bodies when they unite to form com- 
pounds; thus, for example, if carbon and hydrogen 
unite, it is possible we may have three different com- 
pounds ; one containing charcoal carbon, a second plum- 
bago carbon, a third diamond carbon ; or, if we desig- 
nate these respectively as Oa, (7/3, Cy, we may have 

CaH...c$H...c y H; 

and perhaps, as M. Millon has suggested, carbureted hy- 
drogen gas and otto of roses, which have the same con- 
stitution, differ in the one containing charcoal and the 
other diamond. 

These peculiarities are known under the name of allo- 
tropic states, and the phenomenon itself under the des- 
ignation of allotropism. 



LECTURE XXXVIII. 

Chemical Affinity. — Phenomena accompanying 
Chemical Affinity. — Disturbance of Temperature. — 
Production of Light. — Evolution of Electricity. — 
Change of Color. — Change of Form. — Change of 
Chemical Properties. — Change of Volume and Den- 
sity. — Tables of Geoffroy. — Measure of Affinity. — 
Disturbing Causes. — Catalysis. 

By chemical affinity we mean the attraction of atoms 
of a dissimilar nature for each other, an attraction which 
is exhibited upon the apparent contact of bodies. 

How may an allotropic change be impressed on chlorine? What 
are the allotropic states of iron ? Are the peculiarities continued in 
their compounds ? What is meant by chemical affinity ? 




CHEMICAL AFFINITY. 213 

There are certain striking phenomena which very fre- 
quently accompany chemical action. They are the evo- 
lution of Light, Heat, and Electricity ; and, as respects 
the bodies engaged, they may exhibit changes of color, 
of form, of volume, of density, or of their chemical prop- 
erties. 

If in a glass vessel, a, Fig. 180, a mixture of strong 
sulphuric acid and water be stirred together jp^.iso. 
by means of a tube, 5, containing some sulphur- 
ic ether, so much heat will .be evolved by the 
acid and water as they unite, that the ether 
will be made to boil rapidly. 

If upon some water contained in a shallow 
dish, Fig* 181, a piece of potassium be thrown, 
the potassium decomposes the water with 
the evolution of a beautiful lilac flame. 

As respects the evolution of electricity 
during chemical action, the Voltaic bat- 
tery, and, indeed, all Voltaic combinations, 
are examples. In the simple circle we 
have already, in Lecture XXIX., traced the production 
of electricity to the decomposition of the water. 

We have observed that the evolution of Light, Heat, 
and Electricity is not the only phenomenon to be re- 
marked during the play of chemical affinity; the ponder- 
able substances themselves undergo changes. 

If in a glass containing litmus water a drop of sul- 
phuric acid be poured, the blue color of the litmus is at 
once changed to a red, and if into the reddened liquid 
so produced a little ammonia be poured, the blue color 
is restored. This simple experiment is of considerable 
interest, for the reddening of litmus is commonly re- 
ceived as one of the attributes of acid bodies, and the 
restoration of the blue color of those belonging to the 
alkaline type. 

On adding to a solution of sulphate of copper a small 
quantity of ammonia, a pale green precipitate is thrown 
down ; a greater quantity of ammonia redissolves this 
precipitate, and gives rise to a splendid purple solution. 

What phenomena accompany chemical action ? What changes 
are exhibited by the bodies engaged ? Give examples of the evolu- 
tion of heat, light, and electricity. Give examples of changes of 
color. 



214 CHANGES OP COLOE AND FORM. 

A similar solution of sulphate of copper gives rise, un- 
der the action of a solution of ferrocyanicle of potassium, 
to a deep chocolate-colored precipitate. 

A solution of the nitrate of lead, which is colorless, 
acted on by a solution of iodide of potassium, also color- 
less, gives rise to the production of a beautiful yellow 
precipitate, the iodide of lead. 

And, lastly, if sulphuric acid be placed in a solution 
of a soluble salt of lead, or of baryta, a white precipitate 
at once goes down. 

These are all instances of changes of color, and such 
changes are of the utmost importance in practical chem- 
istry, inasmuch as the art of testing depends, for the 
most part, upon a knowledge of them. 

Changes of form in the same manner are exhibited ; 
thus, when gunpowder explodes, a large proportion of 
the ingredients, from being in the solid, escapes in the 
gaseous state. If upon fragments of chalk, carbonate 
of lime, we pour hydrochloric acid, a violent efferves- 
cence takes place, due to the escape of carbonic acid, 
which, from being in the solid, assumes the gaseous 
form. 

The converse of this is sometimes seen, vapors pass- 
im. 182. i u £ nl ^° ^ ne s °Ud state. In the glass a, Fig. 
182, place some strong hydrochloric acid, and 
in b some strong ammonia ; both these bodies 
yield vapors at ordinary temperatures in abun- 
dance, and those vapors, meeting in the air 
over the glasses, give rise to a dense fume, or 
smoke, which, if examined, proves to be solid 
sal ammoniac. 
1^.183. Very often change of form is accompanied 
by change of color ; thus, if under a large bell 
jar, Fig. 183, there be placed a wine-glass 
containing a few copper or iron nails and ni- 
tric acid, a gas of a deep orange color makes 
its appearance, filling the whole bell. 

Perhaps no better instance of an entire 
change of properties could be cited than that 
of the combustion of phosphorus in atmospheric air. 

On what does the art of testing depend? Give an example of the 
production of a gas from a solid, and of a solid from gases. 





CHANGES OF PROPERTIES. 



215 



Fig. 184. 



This substance phosphorus is a body of a waxy appear- 
ance, possessing so great a degree of com- 
bustibility that it requires to be kept un- 
der the surface of water to prevent the 
action of the air. If a piece of it be set 
on fire beneath a clear and dry bell-jar, 
as shown in Fig. 184, it unites with great 
energy with the oxygen of the included 
air, producing white flakes, which, as the . 
combustion is ceasing, descend in the jar, 




giving a miniature representation of a fall of snow. On 
collecting some of this phosphoric snow, its properties 
will be found to be in striking contrast with the phos- 
phorus which produced it ; for instance, far from being 
unacted on by water, it has such an intense affinity for 
that substance that it hisses like a red-hot iron when 
brought in contact with it. It reddens litmus solution, 
and possesses the qualities of a powerful acid. Nor is 
the change confined to the phosphorus ; if we examine 
the air in which it was burned, we find it has lost its 
quality of supporting combustion. 

Changes of volume, and, consequently, changes of 
density, constantly attend chemical action ; a pint of 
water and a pint of sulphuric acid, mixed together, 
farm less than two pints ; and the same may be ob- 
served of alcohol and water. 

When to two substances already in union a third, 
having a stronger affinity for one of the other two, is 
presented, decomposition ensues. Thus, if to the car- 
bonate of soda nitric acid be presented, the soda and ni- 
tric acid combine, and the carbonic acid is driven off in 
the form of a gas. And, again, if upon the nitrate of 
soda so produced sulphuric acid be poured, the nitric 
acid is driven off, and sulphate of soda results. It was 
at one time thought that, by examining a number of 
such cases, we might discover the order of affinity of 
bodies for one another and arrange them in tables; 
these are sometimes called the Tables of Geoffroy. 
Thus the table 

What are the changes which phosphorus undergoes when burned 
in the air? Give an example of change of volume and of density. 
Under what circumstances does decomposition take place? What 
are the Tables of Geoffroy ? 



216 MEASURE OF CHEMICAL AFFINITY. 

Soda. 



Sulphuric Acid, 
Nitric " 

Hydrochloric " 
Acetic " 

Carbonic " 



presents us with the order in which a number of acids 
stand in relation to soda, the most powerful being the 
first on the list, and the salt which results from the 
union of any one of those acids with the soda can be 
decomposed by the use of any other acid standing high- 
er on the list. 

But it is now known that these tables are far from 
representing the order of affinities ; a weaker affinity 
often overcomes a stronger by reason of the interven- 
tion of disturbing extraneous causes ; and tables so con- 
structed lead, therefore, to contradictory conclusions. 
Some very simple considerations may illustrate this. 
Potassium can take oxygen from carbon at low temper- 
atures, or, in other words, decompose carbonic acid gas, 
but it by no means follows- that the affinity of potassium 
for oxygen is greater than that of carbon, and accord- 
ingly we find that at higher temperatures carbon can 
take oxygen from potassium. Indeed, under the influ- 
ence of heat, light, and electricity, we find all kinds of 
chemical changes going on, and in the same manner the 
condition of form exerts a remarkable influence in these 
respects, so that cohesion and elasticity may be placed 
among the predisposing causes producing chemical re- 
sults. If a number of bodies exist in a solution togeth- 
er, they will at once arrange themselves in such a way 
under the influence of cohesion as to produce insoluble 
precipitates, if that be possible; or, under the influence 
of elasticity, to determine the evolution of a gas; if the 
carbonate of soda be decomposed by acetic acid, it by 
' no means follows that the latter has the stronger affinity 
for soda, the decomposition being probably determined 
by the fact that the carbonic acid can take on the elas- 
tic form and escape away as a gas. The sulphate of 

How may it be shown that these are not the tables of affinity ? 
What may be enumerated among these disturbing causes? What 
is the influence of cohesion? What is the influence of elasticity ? 
Give examples of the action of these disturbing agencies ? 



CATALYSIS. 217 

soda may be decomposed by baryta, the cause of the 
decomposition being probably due to cohesion, for the 
sulphate of baryta which results is. a very insoluble 
body. We have, therefore, no true measure of affinity, 
for the relation of bodies in this respect changes with 
external conditions, and the Tables of Geoffroy are only 
tables of the order of decompositions, but not of the or- 
der of affinity. 

Catalysis is a term which was first employed by Ber- 
zelius to explain those cases in which two bodies are 
caused to unite by a third, which itself suffers no change. 
This is also called action by presence. In the produc- 
tion of oxygen from chlorate of potassa and black oxide 
of manganese, the latter substance, while it causes the 
action to go on at a lower temperature, itself remains 
unchanged. In the same manner, platinum black will 
cause the union of hydrogen and oxygen. 

What do the Tables of Geoffroy express ? What is meant i>y cat- 
alysis ? Give examples. 

K 



PART III. 

INORGANIC CHEMISTRY. 



LECTURE XXXIX. 

Pneumatic Chemistry. — Ancient Opinions on the Con- 
stitution of Gases. — Doctrine of the Unity of the Air. 
— The Pneumatic Trough. — TJie Gasometer. — TJie 
Mercurial Trough. — Oxygen. — Modes of Prepara- 
tion. — Properties. — Origin of its Name. — Relations 
to Atmospheric Air and Combustion. — Burning of 
Metals. 

In the catalogue of the elementary bodies of the an- 
cients four substances were enumerated — earth, air, fire, 
and water. Of these, three are now known to be com- 
pounds, and the fourth a state into which bodies are oc- 
casionally thrown. Modern researches have shown that 
there are about 68 different elements. 

For a length of time it was supposed that the various 
exhalations and vapors were nothing more than vitiated 
forms of atmospheric air ; and though, from time to 
time, first one and then another of the gaseous bodies 
was discovered, chemists were slow to admit that they 
were any thing more than modifications of one common 
principle. Thus Roger Bacon, in the thirteenth centu- 
ry, discovered one of the carburets of hydrogen, and 
Van Helmont, in the sixteenth, carbonic acid. The in- 
visibility of these bodies — their remarkable chemical re- 
lations in extinguishing flame and producing death — the 
great mechanical force to which they often gave rise 
when generated in pent-up vessels — their occurrence in 
mines, the bottom of wells, in church-yards, and lonely 
places, suggested to a superstitious mind a supernatural 
origin, and Van Helmont gave them the name of gas, 
which signifies a ghost or spirit. 

What opinions were formerly held respecting the different gases? 
What was the original meaning of the term gas? 



THE PNEUMATIC TROUGH. 



219 



But it is to the researches in the properties of fixed 
air, or carbonic acid, which Black made in 1757, that 
pneumatic chemistry owes its origin. These were soon 
followed by the discoveries of Priestley, Scheele, and 
others. That of oxygen gas by the former of these 
philosophers in 1774 forever destroyed the ancient no- 
tion of vitiated airs, for this gas can support combustion 
and respiration far better than the atmosphere. It may 
be said that modern chemistry dates its origin from the 
discovery of oxygen gas. 

For the purpose of confining gases and manipulating 
with them, a contrivance of Priestley's, the pneumatic 
trough, Fig. 185, is of continual use. It consists of a 



Fig. 185. 




water-tight trough or box, in which a shelf is placed at 
a distance of an inch or more under the level of the con- 
tained water. The jars to hold the gases are filled with 
water, and placed mouth downward on this shelf. When 
gas is disengaged from materials contained in a retort, 
the end of the retort neck is caused to project under the 
mouth of one of the jars, and the gas rises, bubble by 
bubble, eventually filling the jar. When that is accom- 

By whom was the doctrine of the plurality of gases established ? 
Who invented the pneumatic trough? Describe it. How arc the 
jars filled ? 



220 



GASOMETER AND MERCURIAL TROUGH. 



plished the jar may be moved to one side, or, a plate 
being inserted under its mouth, it may be taken out of 
the trough altogether, as at J3. 

"When large quantities of gas are to be preserved, a 
gasometer, Pig. 186, is employed. It consists of a large 

Fig. 186. 




Fig. 187. 



cylindrical vessel, counterpoised in a tank of water by 
the aid of chains and weights. Two pipes open into it 
below, one to bring in the gas from the factory, the 
other to distribute it where wanted. As gas accumu- 
lates, the cylindrical vessel rises out of the water more 
and more, until, when its lower edge is on the surface, 
it is full. The water is kept from freezing in winter by 
the aid of jets of steam. 

As all gases are more 
or less soluble in wa- 
ter, and some to such 
an extent that they can 
not be collected over 
that fluid, the mercu- 
rial trough, Fig. 187, 
has occasionally to be 
employed. It is in all 
respects similar to the 
pneumatic trough, ex- 
cept that its size is 
Describe the gasometer. What is the use of the mercurial trough ? 




PKEPARATTON OF OXYGEN. 



221 



limited by the expense and weight of the quicksil- 
ver. 

Oxygen. 0=8. 

Oxygen gas is probably the most abundant of the 
elements. It constitutes about one third of the weight 
of the solid mass of the earth, eight ninths of that of 
the waters of the sea, and one fifth of the volume of the 
air. A simple mode of preparing oxygen is to place in 
a retort, a, Fig. 188, some red oxide of mercury, con- 

Fig. 188. 




Fig. 189. 



necting with the retort a receiver, 5, from which there 
passes a bent tube, c, dipping below the water of a pneu- 
matic trough, g. On raising the temperature by a lamp, 
the oxide is decomposed into metallic mercury and oxy- 
gen gas ; the former distills into the receiver, 5, and the 
latter collects in the inverted jar in the trough. This 
was the process resorted to by Priestley. 

It may also be readily procured by heating in a flask, 
a, Fig. 189, a mixture of 1 part 
of peroxide of manganese and 3 
parts of powdered chlorate of po- 
tassa. To the mouth of the flask 
a tube, 5, is adapted by means of 
a tight cork, the lower end of the 
tube dipping beneath a jar, c, on 
the pneumatic trough. On rais- 
ing the temperature of the flask by a spirit-lamp, oxygen 
is freely evolved. It is derived from the chlorate of 
potassa altogether, the peroxide of manganese merely 

What limits its size? In what bodies does oxygen occur? De- 
scribe its preparation from red oxide of mercury ; from chlorate of 
potassa. 




222 PEEPAEATION OF OXYGEN. 

acting by presence (catalysis). The change is as fol- 
lows : 

KO+CW^KCl+O,, 
that is, chloride of potassium arises, and six atoms of 
oxygen are given off. One ounce of the chlorate will 
yield about two gallons of the gas. A mixture of chlor- 
ate of potassa with one tenth its weight of sesquioxide 
of iron also yields oxygen with facility and at a low 
temperature. 

On a large scale oxygen is prepared by heating per- 
oxide of manganese (Mn 2 ) to a red heat in a wrought 
iron bottle or retort. One pound, if pure, will yield five 
gallons of the gas, the manganese parting with about 
one third of its oxygen. 

It may. also be produced by heating a mixture of bi- 
chromate of potassa and sulphuric acid, or peroxide of 
manganese and sulphuric acid. 

Oxygen gas may be procured directly from the at- 
mosphere by the aid of baryta. If a current of air con- 
taining a small amount of water, and free from caibonic 
acid, be passed over baryta heated to a low redness, it 
absorbs oxygen and becomes peroxidized. After a time 
the current of air is to be shut off and the temperature 
raised, when the baryta is reduced again to the condi- 
tion of protoxide, and oxygen is given off. The opera- 
tion may then be repeated. A pound of baryta will 
yield nine gallons of pure oxygen gas. 

This gas can also be obtained by passing the vapor 
of sulphuric acid through a porcelain tube heated to 
redness. The products are oxygen, water, and sulphur- 
ous acid. The sulphurous acid is removed by passing 
it through a solution of carbonate of soda, sulphite and 
bisulphite of soda arising. The latter is valuable in the 
arts for the removal of chlorine. A fluid ounce of sul- 
phuric acid produces 360 cubic inches of oxygen. 

Oxygen is a colorless, inodorous, and insipid body. 
It is a non-conductor of electricity, and has the least re- 
fractive power of any of the gases. Its' specific gravity 
is greater than that of air in the proportion of 1.1057 
to 1.000. It is 16 times as heavy as hydrogen. One 

Describe its preparation from peroxide of manganese. How is 
oxygen prepared by the aid of baryta ; of sulphuric acid ? What 
are its leading physical properties? What is its specific gravity ? 



COMBUSTION IN OXYGEN. 



223 



hundred cubic inches of it weigh 34.24 grains. It is a 
powerful electro-negative element, and is the most mag- 
netic of all gases. It has never been condensed into the 
liquid form. 

It is slightly soluble in water, 100 cubic inches of wa- 
ter at 60° dissolving 3 cubic inches of it. Upon this 
supply all water-breathing animals depend for the aera- 
tion of their blood. 

Oxygen is a neutral gas, not altering the tint of blue 
or red litmus water, but it gives rise, on uniting with 
many other bodies, to powerful acids. 

Atmospheric air owes its power of supporting com- 
bustion and respiration to the presence of oxygen. If 
a stick of wood with a spark on the end be plunged 
into this gas, it bursts out at once into a flame. A 
piece of tow saturated with ether, if inflamed in oxy- 
gen, causes an intense combustion throughout the jar. 

A lighted taper, Fig. 190, immersed in oxy- Fig.m. 
gen, consumes away rapidly, the wax itself, in a O 
melted state, burning as well as the wick. The 
combustion, however, soon comes to an end. and 
the taper dies out, because of the production of 
carbonic acid from the union of the oxygen with 
the carbon of the candle. 

If a piece of charcoal-bark in an ignited state 
be put in a vessel of oxygen, Fig. 191, the combustion 
is greatly accelerated, and a multitude of 
scintillating fragments are thrown off. 
When the charcoal dies out, a little lime- 
water poured into the vessel and shaken 
becomes white, from the production of 
carbonate of lime by the union of the car- 
bonic acid which had arisen during the 
burning, with the lime. 

Sulphur burns in oxygen with a beautiful 
purple flame, becoming converted into sulphur- 
ous acid (S0 2 ). If the jar be placed in a dish 
of water tinged with blue litmus, the liquid 
will gradually redden as the acid is produced. 

Many substances commonly regarded as in- 
combustible burn with brilliancy in oxygen. If 

Describe its effect on a lighted stick ; on a taper ; on charcoal 
bark. What is its effect on burning sulphur ? 




Fig. 191. 




Fig. 192. 




224 



COMBUSTION IN OXYGEN. 



a piece of iron wire be coiled into a spiral, Fig. 192, and 
a fragment of ignited wood attached to its lower part, 
on immersing it in oxygen the iron takes fire, white-hot 
Fig. 193. beads of oxide of iron accu- 

mulating and falling off from 
the end of the wire. It is nec- 
essary to put water in the bot- 
tom of the jar, to prevent the 
heated globules melting their 
way through. 

A stream of oxygen from a 
gas-holder being thrown upon 
an iron nail made red-hot in 
the flame of a spirit-lamp, Fig. 
193, causes the iron to burn 
with rapidity, emitting a show- 
er of sparks. By the same means a platinum wire may 
be fused. 




LECTURE XL. 

Oxygen continued. — DrummoncPs Light. — Combus- 
tion of Phosphorus and Zinc. — Changes during 
Combustion. — Lavoisier } s Doctrine. — Oxides, Basic, 
Lndifferent, and Acid. — Physiological Relations of 
Oxygen. — Supporter of Combustion and Combusti- 
ble. — Flame. — Constancy of Heat evolved. — Vege- 
table Production of Oxygen. — Ozone. — Properties. — 
Production. — Detection. — Antozone. 

If a piece of lime be placed in the flame of a spirit- 
lamp through which oxygen is directed by a blowpipe, 
the lime emits a light of such brilliancy that the eye 
can scarcely bear it. This is known as the Drummond 
light. A much more intense light is produced where 
a stream of ignited oxygen and hydrogen is thrown 
upon the lime, the calcium lights used in open-air illu- 
minations being produced in this way. 

A vivid light also originates Allien phosphorus is 
burnt in oxygen, Fig. 194. If the spoon in which the 

What is its effect on an ignited iron wire ? What is the Drum- 
mond light ? What are the phenomena of combustion of phosphorus 
in oxygen ? 



Lavoisier's theory. 225 

melted phosphorus is contained be shal- Pin 194 
low, the entire interior of the jar becomes xf^fllfiW 
rilled with flaming phosphorus vapor, /fj§|§ 
and the effect upon the eye is the same j «i| 

as that caused by looking at the sun. fc > 
The white flakes which fall like a minia- WSJ V 
ture snow-storm in this experiment con- y^^^^^^s 
sist of phosphoric acid (JP0 5 ). . If they ^^^^^J 
are scraped from the interior of the jar ^2^^-222^ 
and dipped into water, a hissing sound is heard, caused 
by the intense affinity of the acid for water. 

Pieces of zinc foil or shavings of that metal, if tipped 
with sulphur and introduced lighted into oxygen, burn 
with an intense green light, the oxide of zinc (Zn 0) 
being formed. 

When any combustible is burned in oxygen two phe- 
nomena are witnessed — a change in the oxygen, and a 
change in the combustible. A piece of charcoal, for ex- 
ample, wastes away, and the gas in which it is burning 
loses the power of supporting combustion. Until the 
time of Lavoisier, it was supposed that burning was due 
to the escape of a substance, phlogiston, from bodies. 
He proved that there is no loss of weight, but that the 
products of combustion weigh just the same as the com- 
bustible and oxygen taken together. He supposed that 
no combustion could go on without oxygen, an idea 
now known to be erroneous, for many substances, as 
phosphorus, antimony, brass, iron, will burn in chlorine, 
their respective chlorides being formed. Bromine and 
vapor of sulphur will also support combustion. 

In Lavoisier's system of chemistry oxygen was re- 
garded as being the essential principle of acidity, and 
hence received its name (from oxus, acid, and gennao, 
to form). But many acids do not contain oxygen, as, 
for instance, hydrochloric acid (HCl). It has since 
been said that there was no strong acid which did not 
contain hydrogen, and that therefore that body was 
more truly the acid former ; but this statement is also 
untrue, fluoboric (BF^) and fluosilicic acid (SiF 3 ) be- 
ing illustrations. 

Describe the burning of zinc. What changes take place in the 
oxygen and the burning body during combustion? What was La- 
voisier's theory of combustion ? 

K2 



226 PHYSIOLOGICAL RELATIONS OF OXYGEN. 

To the compounds which arise from the union of oxy- 
gen with other bodies the designation of oxides is given. 
There are three classes : 1st. Basic oxides ; 2d. Indiffer- 
ent oxides ; 3d. Acids. The following oxides of man- 
ganese furnish good examples of these classes: 

Protoxide of Manganese MnO \ Bagic 0xides- 

Sesqmoxide " Mn 2 3 ) 

Deutoxide " Mn0 2 Indifferent Oxides. 

Manganic Acid.. ; Mn0 3 \ Acids 

Permanganic Acid.. Mn 2 0^ 

From which it may be inferred that among the oxides 
of an electro-positive body, the most powerful base is 
that containing one atom of oxygen ; that as the quan- 
tity of this element increases, indifferent bodies may be 
formed — that is to say, those in which neither basic nor 
acid qualities are well marked ; and in a still further in- 
crease, acids are produced. In this respect the original 
idea of Lavoisier is substantiated to some extent. 

In its physiological relations, oxygen, which forms 
about one fifth of the atmospheric air, is a most interest- 
ing body. It is for the purpose of introducing this el- 
ement to the interior of the system that the respiratory 
mechanism of animals is necessary. The form of the 
apparatus may vary, from the gills in fish to the lungs 
in man, but the object is in each the same. The gas in- 
troduced into the body arterializes the blood, and, unit- 
ing with combustibles, such as carbon, hydrogen, phos- 
phorus, sulphur, produces the various manifestations of 
force that are exhibited — muscular motion, intellectual 
operations, etc., and serves, at the same time, to keep up 
the temperature to a standard point (98° in man), a con- 
dition essential to the well-being of the individual. The 
heat, light, or other force set free in such cases, or in the 
combustion of fuel, has all originally been derived from 
the sun and stored up in the structures of plants. The 
desire for eating so continually felt by animals does not 
arise from a mere wish to gratify the appetite, but from 

What is the relation of oxygen to acid and basic bodies? What 
is the generic designation for its compounds? What are the three 
classes of compounds it yields? What is the respiratory mechanism 
for ? What effect does oxygen produce in the body ? Whence does 
the desire for eating arise? 



FLAME. 



227 



the necessity of securing a fresh supply of force-produc- 
ing material. 

The terms supporter of combustion and combustible 
are expressive of an erroneous idea. No substance is 
intrinsically either one or the other. Hydrogen will 
support the combustion of a jet of oxygen just as well 
as oxygen will that of a jet of hydrogen. In fact, both 
bodies are equally engaged in producing the result, com- 
bustion only taking place on the mutual surface of con- 
tact. Oxygen has come to be regarded as the principal 
supporter of combustion, because most combustions take 
place in the air, which owes its active qualities to this 



Fig. 195. 




An ordinary flame is not incandes- 
cent throughout, but is a mere super- 
ficies or luminous shell, as may be 
seen on lowering a wire gauze down 
upon it, as in Fig. 195. In such a 
flame several distinct parts may be 
traced. Around the wick, a, Fig. 
196, at the points i i, the light is of a 
blue color, for here, the air being in 
excess, the combustion is perfect. From this toward c 
the combustible matter predominates, and the Fig. 196. 
■ light is most intense. A faint exterior cone, 
e e, surrounds the more luminous portion, but 
the interior at b is totally dark. It is proba- 
ble that the light arises chiefly from the igni- 
tion of solid matter, for incandescent gases are 
only faintly luminous. The hydrogen of the 
flame is first burned, and for a moment carbon 
is set free in the solid form at a very high tem- 
perature, its oxidation instantly ensuing. The 
temperature of the oxy- hydrogen flame is 
8061°, but this is surpassed in heat by the 
Voltaic arc. The colors that substances communicate 
to flames furnish the means of ascertaining their pres- 
ence by spectrum analysis (Lecture XVIII.). 

A given weight of a combustible always yields a con- 
stant amount of heat. It does not matter whether the 

Why are the terms supporter of combustion and combustible erro- 
neous ? What is the structure of a flame ? Why do the different 
regions of a lamp flame differ in luminous power ? 




228 OZONE. 

combustion be accomplished in a few minutes or re- 
quires a year ; an iron wire yields as much heat in rust- 
ing slowly as in being burnt in oxygen. A fixed quan- 
tity of oxygen can only produce a certain amount of 
heat, but different combustibles require very different 
proportions of it to effect their complete burning. One 
pound of hydrogen requires 8 pounds of oxygen ; one 
of sulphur only 1 of oxygen. 

The most frequent products of oxidation, both in ani- 
mals and flame, are . carbonic acid and water, and it 
might be supposed that these would eventually accu- 
mulate in the air to such an excess that living beings 
could no longer exist. Plants, however, continually cor- 
rect this tendency. They take those oxidized products, 
decompose them under the influence of the yellow ray 
of light (a fact shown by Professor J. "W. Draper), ap- 
propriate their carbon and hydrogen, and set the oxy- 
gen free once more to run the same course. This de- 
oxidizing power of vegetable matter was discovered by 
Priestley, who found that green leaves, placed in a flask, 
Fig.m. Fig. 197, containing water saturated with car- 
Jjjjk bonic acid, if put in the sunshine, liberated bub- 
BJJIII -bles of a gas rich in oxygen. In the dark no 
lijl¥ such effect took place. 

My Ozone. — Oxygen gas exists in two different 
jj|§j states, a passive and an active. In this latter it 
<§£> is called Ozone, from its peculiar phosphoric 
odor. Ozone is produced when electric sparks are 
passed through pure dry oxygen, or when water is de- 
composed by a Voltaic current, or when phosphorus is 
allowed slowly to oxidize in damp air. It will also 
originate from the slow oxidation of ether. A mixture 
of two parts of permanganate ofpotassa and three parts 
of sulphuric acid will give off ozone for months. 

Ozone is insoluble in water, alcohol, and ether. It 
has intense bleaching and oxidizing powers, attacking 
substances that ordinary or passive oxygen leaves un- 
touched. It decomposes iodide of potassium, the proto- 
salts of manganese, cyanide and ferrocyanide of potas- 

Is there any 'difference in the amount of heat evolved in rapid and 
slow combustion ? Why should the air become unfit to support life ? 
How is this tendency compensated ? What is Ozone ? How is it 
produced ? What are its properties ? 



PREPARATION OF HYDROGEN. 229 

siurn, and oxidizes silver, metallic arsenic, and antimony. 
It is reconverted into oxygen by a heat exceeding 450°, 
but loses its characteristic properties on being subject- 
ed to a much lower temperature or to certain hydro- 
carbons. 

The presence of ozone may be detected by slips of 
paper impregnated with iodide of potassium and starch, 
which become brown, and, on being wetted, assume 
shades of color varying from pink to blue. 

Schonbein states that ozone itself exists in two differ- 
ent states, positive and negative, and calls the former 
Antozone, but the difference is not well marked. 



LECTURE XLI. 

Hydrogen. — Preparation, — Properties, — Effect on 
Sounds, — Combustibility. — Lightness. — Balloons. — 
Explosive Combustion. — Musical Combustion. — Wa- 
ter always produced. — Oxyhydrogen Blowpipe. — Hy- 
drogen a Metal. 

Hydrogen. H—l. 

The name of this gas is derived from udor, water, 
and gennaO) to produce. It forms one ninth by weight 
of all the water on the globe, and is a large constituent 
of animal and vegetable matter. It was at first called 
inflammable air. 

If a piece of potassium be wrapped in paper and rap- 
idly immersed beneath an inverted jar at the water- 
trough, a violent reaction sets in, a gas collects in the 
upper part of the jar, and the potassium, oxidizing, dis- 
solves in the water. The gas produced is hydrogen, 
and the decomposition is shown as follows : 

HO+E=zEO+JI; 
that is, water acted upon by metallic potassium yields 
oxide of potassium and hydrogen gas. 

A more economical process is usually resorted to, de- 
pending on the fact that metallic zinc can decompose 

How may ozone be detected? What is Antozone? What is the 
origin of the name hydrogen ? What was its ancient name ? What 
is the principle of the decomposition of water by potassium ? How 
is hydrogen generally made ? 




230 PREPARATION OF HYDROGEN. 

water at ordinary temperatures. As the oxide of zinc 
produced is insoluble in water and would soon cause the 
action to cease, it is necessary to add an acid, as, for ex- 
ample, sulphuric acid, to unite with the oxide and form 
a soluble salt. The surface of the zinc is then kept clear, 
and the gas is continuously liberated. 

Mg.m. To make hydrogen, a bottle, «, Mg. 198, 

is taken partly filled with water and strips 
of zinc. The mouth of the bottle is closed 
with a cork perforated by two tubes, the 
one, 5, for a funnel, the other, c, for the exit 
of the hydrogen. Through the tube b sul- 
phuric acid is gradually poured until a brisk 
effervescence sets in. The first portions of 
the gas should not be collected, as they are contami- 
nated with air and are explosive. When the action 
slackens more acid must be added. Half an ounce of 
water will produce five gallons of the gas. The chem- 
ical change is thus represented : 

S0 3 , HO+Zn=ZnO, S0 3 +JB". 
Hydrogen may be prepared by substituting iron for 
zinc in the apparatus Fig. 198, or by passing the vapor 
of water over iron turnings heated to redness in a por- 
celain tube. 

As usually prepared it is quite impure, being contam- 
inated with arsenic, sulphur, or phosphorus ; or, if made 
from iron, with an offensive volatile hydrocarbon. When 
obtained from the Voltaic decomposition of water it is 
perfectly pure. 

Hydrogen is a transparent colorless body, having the 
highest refracting power of all the gases. Compared 
with air it is as 6614 to 1000. When pure it has neither 
taste nor smell. It is the lightest known body, one 
hundred cubic inches weighing 2.14 grains — 11,000 
times less than an equal bulk of water. The weight 
of its atom is taken as the standard of other atomic 
weights ; it is therefore 1. It exerts no action on veg- 
etable colors, is only soluble to the extent of 1.5 per cent, 
in water, and has never been liquefied. During experi- 
ments for that purpose, it appeared that there is reason 
to believe that its molecules are smaller than those of 

What is the use of the sulphuric acid? Describe the apparatus 
for its production. What are the properties of hydrogen? 



THE PHILOSOPHER'S LAMP. 



231 



any other body, as it could leak through stopcocks im- 
pervious to other gases. 

In the animal economy hydrogen does not exercise 
any deleterious effect. When respired, it causes the 



Fig. 199. 




Fin. 200. 



voice to assume a feeble, shrill tone 
like that of a child, and a tendency to 
sleep. A bell rung in this gas emits 
a more feeble sound than when ring- 
ing in an air-pump vacuum. If a jar, 
Fig. 199, with a stopCock at its upper 
end, be filled with hydrogen, and, be- 
ing depressed in the water of the 
trough, the cock opened and a- light 
brought near the hydrogen, as it es- 
capes it takes fire at once, 
burning with a pale yel- 
low flame. Or if to the 
mouth of a bottle contain- 
ing the materials for gene- 
rating hydrogen, Fig. 200, 
a cork, through which a 
glass tube is passed, be 
adjusted, and, after allow- 
ing the air in the bottle 
to be displaced to avoid 
an explosion, a light be ap- 
plied to the issuing gas, it 
takes fire and burns in the 
same manner. This is call- 
ed the philosopher's lamp. 
Although the light is faint 
the heat is very great — suf- 
ficient, indeed, to melt fine 
platinum wire. 

The following experi- 
ment proves three facts at 
the same time — 1. The 
lightness of hydrogen ; 2. 
Its inflammability ; 3. That it is not a supporter of com- 
bustion. A jar, a, Fig. 201, is to be filled with hydro- 

What are its relations to respiration ? How may its combustibili- 
ty be shown? Describe the philosopher's lamp. How may its in- 
flammability, its non-supporting power, and its lightness be shown? 




232 



PROPEETIES OF HYDROGEN. 




Fig. 202. 




gen at the water trough, and then, being lifted 
in the air with its mouth downward, a taper 
placed on a wire is carried into its interior. 
As the taper passes the mouth of the jar there 
is a feeble explosion, and the hydrogen, taking 
fire, burns with a pale flame, but as soon as it 
is immersed in the gas it is extinguished. It 
may, however, be relighted, as it is brought 
out of the jar, at the burning hydrogen, and this may 
be repeated several times. The Combustibility of the 
gas, and that it is a non-supporter of combustion, are 
obvious enough. Its lightness is proved by its not 
flowing out of the mouth of the jar, which it would do 
at once if it were heavier than atmospheric air. 

The use of hydrogen for filling bal- 
loons depends on its small specific grav- 
ity. This property is very distinctly il- 
lustrated by filling an India-rubber gas 
bag with hydrogen, and having attach- 
ed to the stopcock a, Fig. 202, a tobac- 
co-pipe, b, by dipping the pipe in a so- 
lution of soap, bubbles may be blown. These rise 
through the air with rapidity, and if a light be brought 
near them they burn with a yellow flame. If the bag 
be filled with a mixture of hydrogen and air, the bub- 
bles will explode violently. 

2^.203. If in a strong brass 

gun, Fig. 203, we place a 
mixture of hydrogen, 1, 
and air, 3, and, hav- Fin 
ing inserted the cork 
tightly, pass a light 
into the touch-hole, 
a violent explosion 
takes place, the hydrogen combining with the oxy- 
gen of the air to produce water, HO* 

Musical sounds originate in vibratory movements 
communicated to the air. If the flame of the philos- 
opher's lamp be covered by the neck of a broken re- 
tort, Fig. 204, a loud sound is emitted. This arises I 

To what use is hydrogen applied on account of its lightness? 
How may this be illustrated on a small scale ? Describe the hydro- 
gen mortar. How may musical sounds be produced by hydrogen ? 




THE OXYHYDROGEN BLOWPIPE. 



233 



from the circumstance that the hydrogen burns in the 
tube, giving rise to a series of small explosions which 
follow each other with rapidity, and these explosions 
throw the air in the tube into vibration. As the tube 
is raised or lowered, the explosions occur with different 
degrees of rapidity, producing sometimes a clattering 
sound and sometimes a pure musical note. 

Whatever may be the circumstances under which 
hydrogen burns — whether quietly in the philosopher's 
lamp, or with trivial explosions as in the tube, or with 
violent detonations, water alone is produced. It may 
be condensed from burning hydrogen by lowering a 
cold porcelain plate upon the flame. During the com- 
bination of hydrogen and oxygen a very great amount 
of heat is given out, for the former combines with eight 
times its weight of the latter, a greater proportion than 
is met with in the case of any other substance. Advan- 
tage is taken of this in the construction of the oxyhy- 
drogen blowpipe, an instrument invented by Dr. Hare, 
which furnishes us with an efficient means of attaining 
a high temperature. There are several different forms ; 
in some the gases are mixed in propel* proportions in a 
strong receiver, and set on fire after passing through a 
Hemming's safety-tube. But it is better to keep them 
in separate reservoirs, on account of the danger of ex- 
plosion, and conduct them to a common jet, where they 
may mix and be burned, as is shown in Fig. 205, where 
the gasometer O contains oxygen and 2^.205. 

H hydrogen; a b are the tubes lead- 
ing to the jet c, where the gases are set 
on fire. By this instrument platinum 
can not only be melted, but even vapor- 
ized. The intensity of the heat de- 
pends, to a great extent, on the fact 
that, unlike ordinary flames, this is sol- 
id — that is, incandescent throughout. 

The flame of hydrogen is very advantageously used 
in detecting the presence of arsenic and antimony, which 
communicate to it characteristic peculiarities (see Ar- 
senic and Antimony). 

What arises from the combustion of Irydrogen ? What is the cause 
of the great heat of burning hydrogen ? Describe Hare's oxyhydro- 
gen blowpipe. What is the peculiarity of the flame ? 




234 WATER. 

In its general relations hydrogen possesses many of 
the properties of a metal, and has hence been regarded 
as one of that class in the vaporous condition. Its trans- 
parency and gaseous form do not militate against this 
conclusion, for the vapor of mercury possesses a similar 
aspect ; but it is to be remarked that it is often replaced 
in combinations by the strongest anti-metal — chlorine. 



LECTURE XLII. 

Water. — Hydrogen Acids. — Water. — Its Composition 
and Properties. — Crystallized Forms. — Compressi- 

. bility. — Synthesis of Water. — Analysis of Water. — 
Its Chemical Relations. — Water of Crystallization 
and Saline Water. — Acts as a basic, indifferent, and 
acid body. — Its Impurities. — Hardness. — Mineral 
Waters. — Peroxide of Hydrogen. — Preparation. — 
Properties. 

Water. 110=9. 

Hydrogen unites with all the electro-negative sub- 
stances, and with many of them forms strong acids, as 
hydrochloric, hydrobromic, hydriodic, hydrofluoric ; 
but with oxygen instead of an acid, a neutral body, 
water, results. Water contains one atom of each of its 
elements, combining to form one atom of water. It is 
therefore a binary compound, and its symbol is HO. 

By volume it consists of two of hydrogen with one 
of oxygen ; by weight, one of hydrogen with eight of 
oxygen. These statements correspond with the first, 
because the hydrogen atom is twice the volume of that 
of oxygen, and the weight of an atom of oxygen is eight 
times that of hydrogen. 

Water is a most important and universally diffused 
substance, covering three fourths of the earth's surface, 
and entering as a constituent into all animal and vege- 
table substances and most minerals. An oyster con- 
tains 81 per cent., and some of the acalephse (jelly-fish) 
99 per cent, of this ingredient. By its aid the processes 

To what class of bodies does hydrogen probably belong ? When 
hydrogen unites with electro-negatives, what class of bodies may 
arise ? What is the constitution of water ? What are the proper- 
ties of water ? 



PROPERTIES OF WATER. 235 

of decay or oxidation necessary to life are caused to go 
on with rapidity ; while, on the contrary, by desiccation 
organic substances may be indefinitely preserved. 

Water is an inodorous, tasteless fluid, of a slightly 
bluish-green color, which conducts heat and electricity 
imperfectly, and refracts light strongly. It freezes at 
32° F., and boils at 212° F. if certain precautions be 
adopted (Lecture XL). In a capillary tube -giro °f an 
inch in diameter it must be cooled to 1°.4 before freez- 
ing, while if a piece of pure ice be heated in a vessel of 
oil, the heat may be continued till the resulting water 
has reached 240°, when the whole is converted into va- 
por with explosion. The specific gravity of water is 
1.000, being the standard of comparison of all other 
liquid and solid bodies. The specific gravity of its va- 
por, steam, compared with atmospheric air, is 1.6219, 
and its color is red. Water is a compressible and elas- 
tic substance. One cubic inch of it at 60° weighs 252.5 
grains, and the cubic foot is so nearly 1000 ounces, that 
the specific gravity of any substance is very nearly the 
absolute weight of a cubic foot of it in ounces. 

If water be slowly frozen it crystallizes in needles, 
crossing one another at angles of 60° and 120°, and pre- 
senting forms of beautiful symmetry, as seen in Fig. 206 
(page 236). Similar flower-like shapes may be seen on 
melting the interior of a block of ice by the aid of a 
beam of sunlight or the electric lamp. 

The compressibility of water is demonstrated and 
measured by an instrument invented by Oersted, in 
which pressure can be exerted upon water in a tube by 
means of a screw. It shows that water is com- Fig.m. 
pressed -^-.^o-o P art °f * ts volume for each atmos- 
phere of pressure. 

The constitution of water was first proved by 
Cavendish and Watt in 1781. It can be illustrated 
in a variety of ways. Thus, if over a jet of burn- 
ing hydrogen a cold glass bell be suspended, Fig. 
207, it becomes soon covered with a misty dew, 
andif the experiment be prolonged, drops of 
liquid finally trickle down the sides, and may be 

What is the specific gravity of water and steam ? What does Fig. 
206 represent? What is the amount of compressibility of water? 
How may the composition of water be synthetically shown ? 



236 



SNOW CRYSTALS. 

Fig. 206. 




caught in a vessel placed to receive them. This liquid 
is water, which has arisen from the union of hydrogen 
with the oxygen of the air. It may be slightly acid, 



SYNTHESIS OF "WATER. 



237 



from the presence of nitric acid produced by oxidation 
of the nitrogen of the air. 

If in a vessel over the mercurial trough twenty meas- 
ures of hydrogen are added to ten measures of oxygen, 
and a small pellet of spongy platinum passed up through 
the quicksilver, union between the two gases rapidly 
takes place, so that it is usual, in order to moderate i^s 
action, to mix the spongy platinum previously with a 
little pipe-clay. As the gases unite the mercury rises, 
until at last they totally disappear. This experiment 
shows that the constitution of water by volume is 2 of 
hydrogen to 1 of oxygen. 

The composition of water by weight was determined 
by Berzelius as follows: Let a flask, a, Fig. 208, con- 



Fig. 208. 




taining zinc and dilute sulphuric acid, be connected by 
a bent tube, &, with another tube, c7, containing chloride 
of calcium. The hydrogen which is evolved from the 
flask consequently deposits any small quantity of water 
it may be contaminated with in the bulbs c c, and then, 
passing through the chloride of calcium tube, c?, is per- 
fectly dried. The tube d is connected with a tube of 
hard glass on which a bulb, 6, is blown. The bulb is 
filled with a known weight of oxide of copper, which 
can be raised to a red heat by the spirit-lamp, h. As 
the dry hydrogen passes over the ignited oxide it re- 
duces it, forming with its oxygen water, and leaving 
pure metallic copper. The water is partly collected in 
the bulb fj and the rest of it is detained by a second 
chloride of calcium tube, g. 

What effect has spongy platinum on a mixture of oxygen and hy- 
drogen ? Describe the method of Berzelius for determining the com- 
position of water by weight. 



238 



COMPOSITION OF WATER. 



If we weigh the tubes e, and/, and g, before and after 
the experiment, it will be found that for every 8 grains 
the oxide of copper, 6, has lost, 9 grains of water have 
been produced, showing that the constitution of water 
by weight is 8 of oxygen to 1 of hydrogen. 

The composition of water may also be proved ana- 
lytically by the aid of the Voltaic battery (Lecture 
XXX.). 

Lavoisier determined the composition of water by 
passing its vapor over fragments of iron made red-hot 
in a tube. Thus, if from the retort a, Mg. 209, contain- 

Fig. 209. 




ing water boiling, steam be passed through a red-hot 
iron tube, c c, filled with turnings of iron or iron wire, 
decomposition takes place, black oxide of iron forming, 
and hydrogen gas escaping by the tube /into the gas- 
holder m n. 

The chemical relations of water are of the utmost im- 
portance. It exerts a more general solvent action than 
any other liquid known, holding in solution gaseous and 
solid substances, acids, alkalies, and salts. As respects 
gaseous bodies, the quantity which water will take up 
depends on pressure and temperature. In the case of 

How may the analysis of water be effected ? Describe Lavoisier's 
method of analysis. What are the chemical relations of water, its 

solvent powers, etc. 



CHEMICAL RELATIONS OF WATER. 239 

salts, an increase of temperature generally increases its 
solvent power. Salt crystals sometimes contain a very 
considerable quantity of it, as in the case of alum, of 
which, if a mass be heated, it melts in its own water of 
crystallization, and after a great quantity of steam is 
thrown off a dry residue remains. Crystals may con- 
tain water in two different states — water of crystalliza- 
tion, which is easily expelled, and saline water, which is 
with difficulty driven off. In works of chemistry, Aq 
(aqua) signifies the former, and HO the latter ; thus 

MO+$0 ? +HO+6Aq 
is the symbol for green vitriol, which is a sulphate of 
the protoxide of iron, with one atom of saline water and 
six of water of crystallization. The saline water is only 
removed by a high temperature, or by being replaced by 
some other body. 

Water unites with many acids with great energy. If 
mixed with sulphuric acid, the temperature will run up 
above 300°. With basic bodies the same results may be 
obtained ; as when quicklime is slaked with water, the 
temperature rises above 570° — more than sufficient to 
inflame gunpowder. Potassa and soda exhibit similar 
phenomena. Toward acids water acts as a base; to- 
ward bases, as an acid ; and toward salts, as an indiffer- 
ent body. 

As found in nature, water is always impure. The 
water of Loch Katrine, in Scotland, has only 2 grains 
of solid matter to the gallon, and that of the River Loka, 
in Sweden, -^ of a grain ; but that from the Great Salt 
Lake has 20,000 grains. Rain-water and melted snow 
contain the various soluble gases that are in the air; 
spring, river, well, and mineral waters, the soluble bod- 
ies of the strata through which they have flowed. From 
these they can be purified by distillation. The solid 
contents in the imperial gallon of some of the principal 
river waters of Europe is as follows : the Thames, at 
Greenwich, 28 ; the Seine, 20 ; the Rhone, at Lyons, 13 ; 
the Danube, at Vienna, 10. Croton water contains 4, 
Schuylkill 4.3, and Boston (Long Pond) 1.2. 

What is meant by water of crystallization and saline water ? How 
is the difference indicated in formula? ? What is the relation of wa- 
ter to acids, bases, and salts ? Is water found pure in nature ? Give 
examples of its constitution. What are the solid contents of Thames 
water, etc. ? 



240 MINERAL WATERS. 

The. quality termed hardness of water results usually 
from the presence of a salt of lime or magnesia. Such 
samples are tested by the aid of a solution of soap in 
alcohol, the quantity required to produce a permanent 
froth being ascertained. 

Mineral waters are usually divided into four groups, 
carbonated, saline, sulphurous, and chalybeate, contain- 
ing respectively in excess carbonic acid, common salt, 
sulphureted hydrogen, and iron. Many also contain ar- 
senic, as the Vichy and Plombieres, waters of France. 
The water of the Congress Spring, at Saratoga, is com- 
posed as follows : 

Chloride of Sodium 390 grains per gallon. 

Iodide of Sodium and Bromide of 

Potassium 6 " " 

Carbonate of Soda 9 " " 

Carbonate of Magnesia " 101 " " 

Carbonate of Lime ., . 104 " . " 

Carbonate of Iron..*. 1 " " 

Silica and Alumina 1 " " 

"612 " " 

Peroxide of Hydrogen. II0 2 =17. 

This compound, the deutoxide of hydrogen, is a defi- 
nite compound of oxygen and hydrogen, and not mere- 
ly oxygenated water. It is prepared by adding a paste 
of peroxide of barium and water to hydrofluosilicic acid. 
The liquid is separated by filtration and concentrated in 
vacuo. It should be kept at a temperature less than 60°. 

It is a colorless, sirupy liquid of a disagreeable taste. 
It bleaches, and is readily decomposed not only by heat, 
but also by several metals and their oxides, and some- 
times with explosion. Peroxide of manganese or lead, 
for example, entirely resolve it into oxygen and water. 

What is meant by hardness of water? How are mineral waters 
divided? What is the composition of Congress water? How is 
peroxide of hydrogen prepared ? What are its properties ? 



PREPARATION OF NITROGEN. 



241 



LECTURE XLIII. 

Nitrogen. — Preparation. — Properties. — Its Indifferen t 
Nature. — Its Combustion and Compounds. — Its Oxy- 
gen Compounds. 

Atmospheric Air. — Constitution. — Methods of Analy- 
sis. — Eudiometry. — Extent of the Atmosphere. — Re- 
lations to Organization. — Pressure of the Air experi- 
mentally shown. 

Nitrogen. ^=14. 

Nitrogen gas is readily procured from the atmos- 
phere by burning phosphorus in a bell jar on the pneu- 
matic trough. If a piece of phosphorus be laid in a cup, 
Fig. 210, and set on fire, all the oxygen in the air of the 
jar, a, will be consumed, white Fig. 210. 

flakes of phosphoric acid (P0 5 ) 
forming, and these being final- 
ly dissolved in the water of the 
trough, c?, there is left behind 
nitrogen contaminated with a 
trace of the vapor of phosphor- 
us. It may be also prepared 
by allowing the phosphorus to 
oxidize slowly at the expense 
of the air. If the interior of a 
jar be wetted and iron filings sprinkled over it, they 
will slowly remove the oxygen from the contained air, 
leaving the nitrogen, if it is subsequently agitated with 
water, quite pure. Copper filings with hydrochloric 
acid may be used in a similar manner. 

To obtain nitrogen perfectly pure, use, instead of the 
phosphorus, Fig. 210, a porcelain vessel containing py- 
'rogallic acid and a strong solution of caustic potassa. 
In this method the carbonic acid of the air is also re- 
moved, and no impurity but vapor of water remains. 

Nitrogen gas (nitron, nitre, and gennao, to produce) 
is a colorless, tasteless, and inodorous body, dissolving 
in water only to the extent of \\ per cent, by volume. 

How is nitrogen prepared by phosphorus? By what other meth- 
ods may it be prepared ? What are the properties of this gas ? 




242 COMPOUNDS OF NITROGEN. 

It is lighter than atmospheric air, its specific gravity be- 
ing .967 ; 100 cubic inches weigh 29.96 grains. It does 
not support combustion nor respiration, and from the 
latter circumstance took the name Azote. It does not 
exert any poisonous agency on animals, as is shown by 
the large proportion in which it exists in the atmos- 
phere. 

Under certain circumstances nitrogen undergoes com- 
bustion, as when electric sparks are passed through air, 
and nitric acid (JST0 5 ) formed. Also, when nitrogen is 
mixed with the detonating compound of oxgyen 1 and 
hydrogen 2, it may easily be oxidized. 

Nitrogen is little disposed to unite with other bodies 
except when either it or they are in the nascent state. 
Its compounds are prone to decompose easily, and hence 
among them we find some of the most remarkable ful- 
minating bodies. The animal and vegetable substances 
into which it enters as a constituent are characterized 
by the facility with which they putrefy or oxidize, and, 
as we shall hereafter find, ferments owe their powers to 
this element. 

Nitrogen unites with oxygen to form five different 
compounds : 

NO, Protoxide of Nitrogen. 
N0 21 Deutoxide of Nitrogen. 
N0 31 Hyponitrous Acid. 
. NO±, Nitrous Acid. 
N0 5 , Nitric Acid. 

With oxygen it also forms atmospheric air ; but this 
is a mixture, and not a compound. 

Atmospheric Air. 

The mechanical properties and constitution of the 
atmosphere are, on account of their great importance, 
first to be described. 

The atmosphere consists chiefly of oxygen and nitro- 
gen, in the proportion of 20.8 volumes of the former to 
79.2 of the latter. It contains, as an essential ingredi- 
ent, also a small proportion of carbonic acid, 10,000 
parts of air containing from 3.7 to 6.2 parts, or, on an 

When does it undergo combustion ? Why does it give rise to ex- 
plosive bodies? Give the compounds of oxygen and nitrogen. Of 
what is atmospheric air composed ? 



ANALYSIS OF AIK. 



243 



average, 5 parts of this gas. Besides these, there are 
variable quantities of the vapor of water, and traces of 
ammonia, sulphureted hydrogen, and carbureted hydro- 
gen. Certain organic constituents, some of which may 
be detected by their odor, give it miasmatic properties, 
causing a variety of diseases. Air is an invisible, elastic 
substance, only seen to be of a blue color in thick mass- 
es, 815 times lighter than water, and is taken as the 
standard of comparison for the specific gravity of gases. 
Its specific gravity is therefore =1. One hundred cu- 
bic inches of it weigh at the mean temperature (60°), 
and pressure (30 inches) about 31 grains. 

There are many methods by which the analysis of 
the air can be effected. The eudiometer, Fig. 211, con- 
sists of a thick glass tube, closed at the upper /r . ^ 
end and open below, where it dips into a cup ^ ' 

or basin of mercury. It is graduated along 
the side, and has two w r ires through the up- 
per part, which approach each other, but do 
not touch. The tube is filled with mercury, 
is then reversed, and a mixture of equal vol- 
umes of air and hydrogen put into it. An 
electric spark being passed between the wires, 
the mixture is exploded. The amount of gas K^? ■ 
left is ascertained by the divisions, and one ^^ 
third of the deficit represents the quantity of oxygen 
originally present. 

The analysis of air may be accomplished by the aid 
of pyrogallate of potassa, and subsequently dry potassa. 
The oxygen, carbonic acid, and aqueous vapor are by 
these means entirely removed. In such volumetric 
analyses errors may arise by variations of pressure, 
temperature, etc., and hence the following method by 
weight is worthy of attention : Air is deprived of its 
carbonic acid and water by being made to traverse 
through tubes containing strong sulphuric acid and 
caustic potassa. It is then passed through a weighed 
tube containing metallic copper heated to redness, which 
deprives it of its oxygen. By connecting the apparatus 
with a glass vessel in a vacuous state, the nitrogen may 

What variable constituents does it contain ? What is its specific 
gravity? How much do 100 cubic inches weigh? Describe the 
eudiometer. By what other methods may air be analyzed ? 




244 



DENSITY OF THE ATMOSPHERE. 



be collected. The increase of weight in the copper 
tube gives the weight of oxygen, while the increase of 
weight in the glass vessel, that was originally vacuous, 
gives the nitrogen. Air is thus shown to be composed 
by weight of 

Oxygen 23.10 

Nitrogen 76.90. 

Its composition by volume has already been stated. 
These proportions remain unchanged, no matter from 
what part of the globe the air may be taken, nor what 
the elevation may be. 

The earth's atmosphere does not extend indefinitely 
into space, but terminates at an altitude of about fifty 
miles ; a fact first discovered by Alhazen, a Mohammed- 
an philosopher. It is therefore a mere film on the face 
of the earth, like the down on a peach, for the globe is 
nearly 8000 miles in diameter. If a representation of 
it were placed on a common twelve-inch globe, it would 
not exceed one sixteenth of an inch in thickness. 

Its relations to the world of organization are full of 
interest. All plants come from it, and all animals re- 
turn to it, so that it stands as the bond of connection 
between the two. It is the grave of animal, the cradle 
of vegetable life. 

As we ascend to the more elevated regions the air 
becomes less dense, for the obvious reason that, as it 
is a very compressible body, those portions of it near 
the earth have to sustain the weight of the mass above, 
and are therefore more dense; but in the higher re- 
gions, where the superincumbent pressure is less, the 
air is more rare, as is shown in the following table : 



Height in Miles. 


Volume of Air. 


Barometric Inches. 





1 


30 


2.705 


2 


15 


5.410 


4 £ 7.5 


8.115 


.8 


3.75 


10.820 


16 


1.875 


13.525 


32 


.9375 


16.230 


64 


.46875 


18.935 


128 


.234375 



What is its composition by weight? To what distance does the 
atmosphere extend ? What are its relations to animals and plants ? 
Why does its density decrease with the altitude ? 



MECHANICAL PROPERTIES OF THE All?. 



245 



This also shows that the great mass of the atmos- 
phere is within a very short distance of the earth's sur- 
face — on e half within three miles, and four fifths within 
eight miles. At different altitudes the temperature va- 
ries, being 1° colder for every 350 feet of ascent, partly 
from the increased capacity for heat, and partly because 
it is warmed mostly by contact with the earth. The 
line of perpetual snow is 15,200 feet above the sea. at 
the equator, 3818 at 60° latitude, and only 1000 at 76°. 
At 85° it has sunk to 117 feet, and nearer the pole act- 
ually dips below the soil. 

Of the constituents of the air, the oxygen and nitro- 
gen are regarded as fixed, the carbonic acid, water, and 
ammonia as variable ; but every process of respiration 
and combustion tends to change the amounts. Animals 
take oxygen and replace it by carbonic acid, while plants 
do the reverse. A strict balancing is, however, observed 
between these various operations, so that no change can 
be detected between the present atmosphere and that 
existing centuries ago. 

Of the mechanical properties of the air, the first to 
which we have to direct our attention is its press- Fig. 212. 
ure, w T hiclr takes effect equally in all directions, 
upward, downward, and laterally. Thus, if we 
fake a glass tube, a, Fig. 212, several feet long, 
closed at one end and open at the other, and, 
having filled it with water, place over the mouth 
a stout piece of paper, 5, and turn it upside 
down, the paper will not fall off nor the water 
flow out. They remain, as it were, suspended 
on nothing, but, in reality, sustained by the upward 
pressure of the air. Or if we take a bottle, a, Fi 213 
Fig. 213, with a hole, £, half an inch in diam- 
eter at the bottom, and, having filled it with 
water, close the mouth with the finger, it may 
be held in the air without the water flowing 
out, though the aperture b is wide open. In 
this instance, again, it is the upward pressure 
of the air which sustains the liquid. 

Advantage is taken of the elasticity and expansibility 

•How does its temperature vary? Which are the variable and 
which the fixed constituents of the air? Give some illustrations of 
the upward pressure of the air. 




2-iG 



THE AIB-PUMP. 



of the air in the construction of the air-pomp, an instru- 
ment intended for the removal of air from closed ves- 
sels. It consists of two cylinders, Fig. 214, the pistons 







of which may be alternately raised and depressed by a 
rack and pinion. They communicate by a tube with the 
interior of a bell-jar or receiver, which stands on the 
air-pump plate* and makes a tight joint with it because 
the two are ground flat. On working the handle the 
air in the bell-jar is, little by little, removed, and event- 
ually only a small fraction of the original amount re- 
mains. Let the glass globe c/, Fig. 215, be nearly filled 
Fig. -215. with water, and inverted so that its neck. &, 
dips beneath the water contained in vessel c. 
If the whole be covered with an air-pump 
receiver, d, and the receiver exhausted, the 
bubble at a dilates, and after a time, as the 
action of the machine continues, fills the en- 
tire glass, both bulb and tube. As the press- 
ure is restored by letting air again into the 
bell-jar, the bubble contracts and eventually regains its 
original size. 

The air-pump enables us to exhibit in a striking man- 
ner the chief mechanical properties of the air. Thus, if 
on the plate of it there be placed a receiver, a. Fig. 2^, 

Describe the air-pump. Describe Fij. 215. Give illustrations of 
downward pressure. 




MECHANICAL PROPERTIES OF THE AIR. 



247 




Fig. 21S. 



as soon as the air is exhausted from its inte- F & 216 - 
rior, the superincumbent pressure retains the 
glass so firmly in contact that it is impossible 
to lift it off; but when the air is readmitted 
it can easily be moved. If within the receiv- 
er a a smaller one, #, be placed, and exhaus- 
tion made, while a is fixed, b can be easily 
moved by shaking the pump; but, on letting in the air, b 
becomes fixed and a loosened. 

If over the mouth of 
a jar, Fig. 217, placed 
on the pump, the palm 
of the hand be laid as 
the air is exhausted, it is 
pressed in close contact 
with the jar, and can 
only be removed by the exertion of a very 
considerable force. 

On the small plate a, Fig. 218, furnished 
0, vvith a stopcock, 5, terminating in a jet, c, 
a tall receiver is placed, and the appara- 
tus being screwed on the air-pump, is ex- 
hausted, and the stopcock closed. On 
being opened when the lower end of the 
tube dips under water, the water rises to 
the top of the jar, and forms a fountain in 
vacuo. 



/f^ 


3jk 


F 


f H 


i! 


1 


\l « 


i! 
[c IJr 


M 


H 


-r~~al 


j>~3 




)h. 



LECTURE XLIV. 

Atmospheric Air. — Pressure of the Air. — Exhaustion 
ivithout an Air-pump,— Determination of the Weight 
of the Air. — Amount of Pressure. — Elasticity of the 
Air. — Air in the Pores of Bodies. — Aquatic Respi- 
ration. — Preservation of Meats and Fruits. 

The Magdeburg hemispheres, invented by Otto Guer- 
icke, who also invented the air-pump, illustrate in a strik- 
ing manner atmospheric pressure. They consist of a 
pair of brass hemispheres, Fig. 219, with handles. They 



Describe the fountain in vacuo, 
spheres ? 



What are the Magdeburg hemi- 



248 



PRESSURE OF THE AIR. 

Fig 219. 





fit without leakage to one another and form. a sphere. 
One of them has a stopcock through which the air may 
be exhausted ; and, on this being done, it will be found 
impossible to pull them apart, though when the air is 
readmitted and the pressure restored to the interior, 
they will fall apart by their own weight. 

If over the mouth of an open receiver, Fig. 220, a 
j%. 220. piece of bladder be tied with a waxed thread, 
when the air is suddenly exhausted the blad- 
der becomes deeply depressed into a spheri- 
cal concavity by the pressure of tRe air, and 
finally bursts inward with a loud explosion. 
It is upon this principle of atmospheric 
pressure that the various instruments for 
cupping act. The simplest method of performing this 
operation is to place the cupping-glass for a moment 
over the flame of a large spirit-lamp, and then transfer 
it rapidly to the skin. As soon as the steam with which 
the interior of the vessel is filled condenses, a. partial 
vacuum is formed, and the soft parts are pressed into 
its interior, 

For many experiments the air-pump is not required. 
Thus, if we take a vial, a, Fig. 221, and 
fit to the mouth of it a cork, 5, through 
which passes a piece of glass tube, c, 
drawn to a narrow jet at one end, but 
open at the other, by placing the finger 
over the opening and introducing it into 
the mouth, the air, by the action of the 
tongue and muscles of the mouth, may be 
drawn out to a great extent ; and when the exhaustion 
has been carried as far as possible, by pressing the fin- 
ger over it the opening may be closed. If now the 

Describe the experiment Fig. 220. How is cupping performed ? 
How may exhaustion by the mouth be illustrated ? 



Fig. 221. 




WEIGHT OF AIR. 



249 



Fig. 222. 



bottle be turned upside down, as at e, in some water, 
and the finger removed, a fountain in vacuo is formed. 
The pressure of the air depends on the fact that it is 
a heavy body, as may be proved 
by weighing it directly. Let 
a light glass flask, a, Fig. 222, 
fitted with a stopcock, be coun- 
terpoised in a balance, then let 
the air be exhausted from it, 
and the loss of weight determ- 
ined. On opening the stop- 
cock and again admitting the 
air, it will regain its original 
weight. A flask containing 100 
cubic inches will in this man- 

Fig. 223. 





ner lose 31 grains in weight, 
and that, therefore, is the 
weight of that amount of air. 
Atmospheric air is used as 
the standard of comparison 
of the specific gravities of 
othe»r gases. The process 
for the determination is very 
simple. A pear-shaped flask, 
F, Fig. 223, furnished with a 
small stopcock' is screwed to 
the air-pump and exhausted 
of air. After being weighed 
it is attached to the gradua- 
ted jar.6r, filled with air or 
any other gaseous body, and, 

the stopcocks being opened, it fills. It is then reweighed, 
How may the weight of air be directly ascertained? How may 

the relative weight of other gases be determined ? 

L2 



250 



ELASTICITY OF THE AIR. 



Fig. 224. 



and will be found to have increased several grains. The 
amount that has passed into the flask is known by read- 
ing off at the graduation. 

There are several different methods of stating the 
amount of the mean pressure of the air ; thus Ave say- 
that it is equal to 15 pounds on the square inch, or to a 
column of mercury 30 inches long, or to a column of 
water 33 feet long. Upon the body of a man the atmos- 
phere presses with a weight of 30,000 pounds, but it is 
not felt because the internal air presses outward with 
similar force. Humboldt exposed his body to a varia- 
tion of pressure equal to 31,000 pounds without suffer- 
ing any inconvenience. 

That air is a highly elastic substance can be readily 
shown. Under a bell-jar, Fig. 224, let there 
be placed a half-blown bladder, the neck of 
which is tied. As the air is removed from 
the bell the bladder distends, but on restoring 
the pressure it becomes as flaccid as it was 
before, showing that the included air expands 
and contracts as the pressure upon it varies. 
This may be still more strikingly shown by 
taking a small India-rubber bag, Fig. 
225, the mouth of which is closed tight- 
ly, and using it instead of the bladder. 
On rarefying the air in the receiver the 
bag begins to dilate, and may be extend- 
ed to several times its original dimen- 
sions, as shown by the dotted line ; but 
when the pressure is restored it returns 
to its former size. 
Nor does the expansion take place with 
an inconsiderable force. If a flaccid blad- 
der be compressed by leaden weights, Fig. 
226, as soon as the pressure is removed it 
will push up the weights. ISTor does it 
lose its elasticity by being long confined. 
Some of the old chemists kept air com- 
pressed in copper globes for months, and 

How may the pressure of the air be stated ? What is the press- 
ure on the body of a man ? How may the elasticity of air be illus- 
trated ? How may it be shown by an India-rubber bag ? Give an 
illustration of the amount of this force. 




Fig. 226. 




INSPIRATION OF FISHES. 



251 



Fig 22S. 





found that, as soon as liberated, it regained its original 
size. 

By taking advantage of the expansion of air, and by 
reducing the pressure, its existence in the pores Fig ^ m , 
of many bodies may be shown ; thus if we place 
an egg, Fig. 227, an apple, or other such objects 
in a glass of water, and exhaust the air from the 
covering bell-jar, w^e shall see bubbles 
of air in countless numbers escaping 
through the water. A glass of ale, 
Fig. 228, placed in an exhausted re- 
ceiver, foams from the escape of. car- 
bonic acid gas; and spring or river 
water, examined in the same way, is found to 
contain three or four per cent, of gas. 

This last fact is of great importance, for it 
is by the aid of this air that all water-breathing animals 
exist. Fish do not respire water, but the air contained 
in it. This air differs from the atmosphere, in contain- 
ing more oxygen — 33 per cent, instead of 21. The 
cause of the difference is that oxygen is more soluble in 
water than nitrogen. Nevertheless, the respiration of 
aquatic animals is never so perfect as that of air-breath- 
ers, on account of the limited sup- 
ply, and hence such animals are al- 
ways cold-blooded. When fish are 
placed in water under an exhausted 
receiver, Fig. 229, they soon die. 
They are unable to descend to the 
bottom except by violent exertion, 
because the air in their swimming- 
bladder expands and buoys them up. 
The highest fishes, as the whale, 
which has a temperature of 98°, 
breathe the atmosphere by lungs, 
coming periodically to the surface 
for that purpose. 

The necessity of air to the support of combustion may 
be demonstrated by the length of time that a candle 

How may the presence of air be detected in the pores of solid 
bodies? How may it be shown that air exists in water? Of what 
use is the air in water ? How does it differ from atmospheric air ? 
How do fishes under an exhausted receiver act ? 



Fig. 229. 




252 



PRESERVATION OF MEAT AND FRUIT. 



Fig. 230. 



will burn in a jar full of air, and in the same jar ren- 
dered vacuous. In the latter case it dies out at once, 
the smoke descending to the bottom of the jar, owing 
to the rarefaction of the surrounding medium. 

Substances prone to decay, such as meats and fruits, 
may be preserved for a long 
time in vessels void of air. 
The process is illustrated in 
Fig. 230. The fruits are placed 
in a jar, closed by a sound 
cork covered with sealing- 
wax. A small hole is made 
through the cork, and the air 
exhausted. When the vacu- 
um is as complete as may be, 
the hole is closed by melting 
the wax in a converging beam 
of sunlight. On the large 
scale, the things to be pre- 
served are inclosed in tin cans, which are sealed by sol- 
dering, except a pinhole that is left through the cover. 
The tins are immersed in boiling water, and when steam 
issues from the pin-hole it is closed by a drop of melted 
'solder. 

From the foregoing experiments and considerations, 
it is demonstrated that the prime fact in pneumatics is, 
that air has weight; from this arise its pressure and 
varying density at different altitudes. Its elastic force 
must also be equal to the pressure upon it ; if it were 
less, the air would compress ; if greater, dilate. 

How may the necessity of air to combustion be shown? How 
may meats, etc., be preserved? What facts in pneumatics have we 
demonstrated ? ♦ 




THE BAROMETER. 



253 



LECTURE XLV. 

Atmospheric Air. — Construction of the Barometer. — 
Cause of its Phenomena. — History of its Invention 
by Torricelli. — JPascaVs Experiment. — Illustrations 
of the Nature of Pressure. — Variability of Pressure. 
— Disturbances in the Composition of the Air. — Are 
corrected by the Winds and Diffusion. — Illustrations 
of Diffusion. — The Air is a Mixture. — Marriotts 
Law. 

If we take a tube of glass, a 5, Fig. 231, more than 
30 inches long, sealed at one end and open at the m 231 
other, and, having filled it with quicksilver, in- 
vert it in a cup of that metal, c, the mercury 
will not flow out of the tube, but will remain 
suspended at a height of from 28 to 30 inches, 
a vacuous space being left at the upper part. A 
scale, dj divided into inches and decimal parts, 
the zero being at the level of the mercury in the 
cup, completes the instrument. It is termed a 
barometer. 

The cause of the suspension of the mercury in 
Fig. 232. the tube is the pressure of the air. This 

may be demonstrated by placing over the ba- 
rometer a tall air-pump jar, Fig. 232, and ex- 
hausting. It will be found that, as the pressure 
is reduced, the column of mercury falls ; and 
when the pressure is restored, it rises again to 
the original point. ^ ^ 233 

The same fact may be proved in an- 
other manner. If a tube upward of 30 
inches in length, the upper end of which 
is closed by a piece of bladder, be filled 
with mercury and inverted in a cup, 
Fig. 233, the bladder will be deeply de- 
pressed, the pressure of the air being borne by it. 
If now a pinhole be made through the bladder so 
as to allow the air to press on the top of the mer- 

Describe the barometer. What are the causes of suspension of 
the mercury? How may this be proved? Describe Fig. 233. 





254 



THE BAROMETER. 



cury, the column descends to the level of that in the 
cup below. 

The barometer was invented by Torricelli in 1643. 
Some plumbers working for the Duke of Florence found 
that it was impossible to make a pump that would raise 
water more than about 30 feet. This fact, coming to 
the knowledge of Torricelli, caused him to suspect that 
water rose in those machines in virtue of the pressure 
of the air, and not from Nature's abhorrence of a vacu- 
um, as was at the time supposed. If the limit to which 
water can be raised by suction is reached when the 
weight of the column of liquid equilibrates the weight 
of the air, a heavier fluid will be raised to a less height. 
Accordingly, a pump ought to raise quicksilver only as 
many inches as water feet, for the respective weights 
are as 1 to 13-J. Torricelli found, by means of a pump 
iixed to a long glass tube, that such was the case. 

That it is the pressure of the air that supports the 
mercurial column is definitely proved by Pascal's exper- 
iment of taking a barometer up a high mountain. As 
the height of air above the instrument is decreased, the 
column of mercury also decreases in height. Advan- 
tage is taken of this fact to determine the height of 
mountains. 

The principle of the barometer may be illustrated by 
Fig. 234. substituting for the pressure of the air the press- 
ure of a column of water. If some quicksilver 
be put at the bottom of a deep jar, a, Fig. 234, 
and a long tube, &, plunged into it, on pouring 
water into the jar, for every 13^ inches in depth 
poured in, the quicksilver will rise one inch, the 
mercurial column counterpoising the column of 
water just as it does the column of air in the 
case of the barometer. 

Mr. Boyle discovered that the pressure of the 
air is variable, the mercurial column sometimes "falling 
to 27 inches, sometimes rising to 30. The range is 
commonly estimated at 2.5 inches. It is less in the 
tropics. These changes are irregular, and depend on 

Who invented the barometer ? What were the circumstances of 
the invention ? What was Pascal's experiment ? How may the 
phenomena of the barometer be illustrated by the pressure of a wa- 
ter column ? What are the irregularities of the barometer ? 




DIFFUSION OF GASES. 



255 



meteorological events. A sudden change in the barom- 
eter is regarded by seamen as indicating an approach- 
ing storm. There are also regular variations during the 
day, the column rising twice in 24 hours. In winter 
the first maximum is about 9 A.M., the minimum at 3 
P.M. ; the second maximum at 9 P.M. 

The pressure of the air and its variations can also be 
measured by an instrument called the Aneroid Barom- 
eter, which consists of an elastic metal box partly ex- 
hausted of air. By the aid of multiplying levers, the 
variations in the size of this box are conveyed to an in- 
dex which plays upon a divided scale, and enables the 
observer to read the amount. It must be graduated by 
a standard mercurial instrument. 

Many causes tend to give rise to local disturbances 
in the air. In its lower strata, combustion and respira- 
tion are tending to diminish the oxygen and increase 
the carbonic acid. On the contrary, vegetation, more 
particularly at the equator, diminishes the carbonic acid 
and increases the oxygen. But, notwithstanding these 
disturbances, and the fact that the constitu- 7^:235. 
ents of the air are of different specific gravi- 
ties, its composition is nearly the same every 
where. This is o^jng partly to the winds 
" and partly to the principle known as the dif- 
fusion of gases, which may be illustrated as 
follows : If two vials, h c, Fig. 235, are rinsed 
out, h with ammonia and c with hydrochloric 
acid, each becomes filled with the vapor of 
the liquid used. On placing them mouth to 
mouth, as in the figure, dense white fumes 
of sal ammoniac (NH 4 C1) appear simultane- 
ously in both. 

The same effect will take place even though 
barriers intervene, as may be shown by tak- 
ing a porous earthenware cup, a a, Fig. 236, 
such as is used in Grove's battery, and ce- 
menting into its mouth *a tube, b. A wide- 
mouthed bottle, c c, being placed as a cover over the 

What are the diurnal variations ? What is the Aneroid ? What 
tends to change the composition of the air? How is the air kept 
uniform in composition? How may diffusion be illustrated? How 
may it be shown to occur through barriers ° 



256 



DIFFUSION THROUGH BARRIERS. 




Fig. 23G. 



porous cup, it may be filled with hydro- 
gen by displacement. If the end of the 
tube be put in water in a cup, .<#, the wa- 
ter will rush up the moment the bottle is 
removed. The hydrogen diffuses out 
through the porous cup. 

Even India-rubber will allow the same 
results to be 



Fig. 23L 

shown. Let a 
bottle, 5, Fig. 
237, be taken, 
and the mouth 
having been 
closed with a 
sheet of India- 
rubber, let it be 
exposed under 
a jar of car- 
bonic acid. It 
swells up, and 

assumes a dome shape, the acid having 
diffused into the bottle. Or, if the bottle be filled with 
carbonic acid, as at a, and exposed to the air, the car- 
bonic acid will diffuse out, and th^Jndia-rubber be de- 
pressed. 

By substances which can not be regarded as having 
Fig. 23s. any pores at all, the same phe- 

nomena are exhibited. In Fig. 
238, a a is a bottle rinsed out 
with ammonia. By means of 
a tube, b 5, a soap-bubble, c, is 
blown in it. If some of the 
air from the bubble be drawn 
into the mouth it will be found 
to have at once acquired an 
ammoniacal taste ; or, if a rod 
dipped in hydrochloric acid be 
presented to the projecting 
end of the tube 5,, copious 
white fumes arise. 
Dr. J. W. Draper showed, by the aid of the apparatus 





Describe Fig. 237. 
be shown ? 



How may diffusion through poreless media 



MARRIOTTE S LAW. 



257 




M 



Fig. 239, that sulphureted hydrogen will dif- 
fuse into atmospheric air, though resisted by 
a pressure of 750 pounds on the square inch. 
It consists of a strong tube hermetically 
sealed at one end, through which a pair of 
platinum wires, b c, pass. The other end, 
a a, is closed by a sheet of India-rubber. The 
gauge-tube, c?, which indicates the pressure, 
carries at its top a little cup to contain ace- 
tate of lead, or any other reagent. On con- 
necting b and c with a Voltaic pile, the wa- 
ter which fills the tube to e e is decomposed, 
and oxygen and hydrogen accumulate in the 
tube, exerting a pressure greater and great- 
er as the decomposition is prolonged. The 
whole apparatus may then be subjected to 
a jar of sulphureted hydrogen. It will be 
found to pass through with facility, coloring 
the acetate of lead solution black or deep 
brown. 

That the atmosphere is a mixture, and not 
a compound, is proved by its easy decomposibility, its 
refractive- power, and by the fact that its constituents 
retain their properties unchanged. The oxygen and ni- 
trogen may be determined as already described : the 
carbonic acid by potassa or lime-water, the aqueous va- 
por by the method for the dew-point. 

Atmospheric air being thus an elastic and compressi- 
ble body, it is necessary to determine the law of F -- ffm 
its change of volume under changes of pressure. 24 °- 
This is known as Marriotte's law, and applies to W& 
many other gases. TJie volume of a gas is in- 
versely as the pressure upon it. This law is of the 
utmost importance in gaseous chemistry. It is il- 
lustrated by the instrument Fig. 240, in which a b 
is. a bent tube, open at a and closed at b. The 
branch a may be several feet long, and b six inch- 
es. A small quantity of mercury is poured into 
the tube so as to occupy the bend, and shut up a 
column of air between d and b. If the tube be filled 

How may diffusion against pressure be demonstrated ? What 
proofs are there that the atmosphere is a mixture ? "What is Mar- 
riotte's law ? How may its truth be proved ? 



258 PROTOXIDE OF NITEOGEN. 

with mercury to the height of 30 inches, the pressure 
of this column is exerted on the air in b ; and as there 
are now the weight of two atmospheres — that of the 
ordinary atmosphere and that of the mercurial column 
— it is compressed into half its former volume, c. If 
we bring upon it three atmospheres, it compresses to 
one third; four, to one fourth. And the law of course 
holds good for diminution of pressure ; reduce the 
pressure one half, the volume doubles, etc. 



LECTURE XLVL 

Compounds of Nitrogen and Oxygen. — .Protoxide of 
Nitrogen. — Preparation and Properties. — Constitu- 
tion. — A Supporter of Combustion. — Physiological 
Effects. 

Deutoxide of Nitrogen. — Preparation and Properties. 
— Constitution. — Relations with Free Oxygen. 

Hyponitrous Acid. — Preparation and Properties. 

Protoxide of Nitrogen. NO— 12. 

■ If nitrate of ammonia be exposed to a temperature of 
^24! 350° in a retort, Fig. 241, it is 

decomposed, being resolved into 
water and the protoxide of ni- 
trogen. The former condenses 
in the neck of the retort, the lat- 
ter rises into the jar. If whitish 
fumes are evolved, they indicate 
that the temperature is too high. 
The decomposition is very simple. 

N0 5 +NH 3 =2(NO) + 3(£TO). 
One atom of the salt yields two atoms of the protoxide 
of nitrogen and three of water. One ounce of the ni- 
trate produces two gallons of the gas. 

The protoxide of nitrogen is a colorless transparent 
gas, having a sweetish taste. It is soluble in water, 
that liquid dissolving about its own volume of the gas, 
but giving it up on being boiled. Its specific gravity is 
1.527. A hundred cubic inches weigh 47.08 grains; it 

How may protoxide of nitrogen be made ? What are its proper- 
ties ? 




ITS PROPERTIES. 259 

is therefore half as heavy again as air, and may be col- 
lected by displacement, the specific gravity being the 
same as that of carbonic acid. It may be liquefied at 
45° by a pressure of fifty atmospheres, and at 150° be- 
low zero freezes into a transparent crystalline solid. In 
the liquid form it is colorless, and boils at —125°, A 
drop of it falling on the skin produces the effect of a 
burn. Mercury sinks in it and freezes into a solid. 
The liquid protoxide mixed with bisulphide of carbon 
produces the lowest temperature yet attained, —220°. 
If the liquid be forced into the air from a jet, a part 
freezes into a solid, the same occurring when it evapo- 
rates in vacuo. It is composed by atom of one of nitro- 
gen and one of oxygen, and by volume of two of nitro- 
gen united to one of oxygen, condensed into two vol- 
umes — a constitution like that of water. As it contains 
half its volume of oxygen, it supports combustion act- 
ively ; a spark on the wick of a taper introduced into it 
bursts into a flame, and phosphorus burns with great 
brilliancy. 

Protoxide of nitrogen, or laughing-gas, as it is popu- 
larly called from the following circumstances, possesses 
remarkable physiological properties. When breathed 
it produces a transient intoxication, owing to the rapid 
'oxidation that is set up throughout the system. It is 
even more active than pure oxygen, because it is more 
readily soluble in the blood, and therefore causes a more 
rapid combustion of the tissues. The individual under 
its influence has a great flow of ideas, an irresistible tend- 
ency to laugh and undergo great muscular exertion, 
and not infrequently becomes pugnacious. This state 
is succeeded by one of depression, on account of the ac- 
cumulation of carbonic acid in the blood, the lungs not 
being able to remove it as fast as produced. The respi- 
ration of the protfkide is not unattended with danger, 
as it may contain chlorine or deutoxide of nitrogen, or 
may dangerously stimulate an excitable constitution, 

Deutoxide of Nitrogen. iVT^— 30. 
The deutoxide or binoxide of nitrogen is made by the 
How may it be liquefied? What are the properties of liquefied 
protoxide? Why does it support combustion?* What are its rela- 
tions to respiration? Why does it intoxicate? What is the cause 
of the subsequent depression ? How is deutoxide of nitrogen made ? 




260 DEUTOXIDE OF NITROGEN. 

action of dilute nitric acid on slips of copper. The nec- 
Fig. 242. essary apparatus is represented in Fig. 242. 
Fresh supplies of nitric acid are occasional- 
ly to be added through the funnel, 5, when 
the action slackens. It is a colorless^ gas, 
and may be collected over water, as that 
fluid only absorbs one twentieth of its vol- 
ume of it. 

It is composed of equal volumes of nitro- 
gen and oxygen, united without condensa- 
tion. Its specific gravity is 1.0365; 100 cubic inches 
weigh 32.10 grains. It does not support combustion, a 
lighted taper, ignited camphor, or sulphur being extin- 
guished ; but if phosphorus in intense ignition be placed 
in it, the combustion is increased in activity. The same 
is true of potassium or sodium. The vapor of bisulphide 
of carbon, mixed with the deutoxide and set on fire, 
causes the evolution of a most intense light, and the pro- 
duction of carbonic and sulphurous acids, with the lib- 
eration of nitrogen. 

SJV0 2 + C8 2 =2$0 2 + C0 2 +sJV. 
Iron, arsenic, some sulphides and sulphites, and proto- 
chioride of tin, decompose it, protoxide of nitrogen be- 
ing liberated. 

The most remarkable quality of deutoxide of nitrogen 
is its action on mixtures containing oxygen, as, for ex- 
ample, atmospheric air. It at once produces red fames 
of nitrous acid, the deutoxide taking up two atoms of 
oxygen. For this reason it has been used to effect the 
analysis of air, certain precautions being adopted. The 
deutoxide must be added in a small steady stream to 
the air ; red fames are produced, which are removed by 
the water of the pneumatic trough. The residual gas is 
less in volume than the air and deutoxide; one fourth 
of the deficit represents the volume tgf oxygen original- 
ly present. 

Solutions of the protosulphate and protochloride of 
iron dissolve this gas, a greenish - black liquid being 
formed. It escapes, however, in a vacuum, leaving the 

Does it support combustion ? What is its action on gaseous mix- 
tures containing oxygen ? How may it be used to determine the 
amount of oxygen ? What are its relations to protosulphate and 
protochloride of iron ? 



HYPONITKOUS AND NITROUS ACIDS. 261 

iron salt unchanged ; heat only partially expels it. The 
deutoxide yields in the spectroscope the red band of ni- 
trogen, and near it one derived from the oxygen. 

Hyponiteous Acid. N0 3 =:38. 

This substance, now frequently called nitrous acid, 
may be made by mixing four volumes of dry deutoxide 
of nitrogen with one of dry oxygen over mercury. 
There arises a green fluid, colorless however at zero, 
which gives off an orange vapor. It may be produced 
from the action of 8 parts of nitric acid on 1 of starch, 
the evolved gases being dried by chloride of calcium, 
and then conducted into a tube cooled to zero. It is 
doubtful whether the acid has yet been produced pure ; 
it is generally contaminated with nitrous or nitric acid. 
Water decomposes it into nitric acid and deutoxide, 

3jsro 3 =zJsro 5 +-2isro 2 . t 

It forms a class of salts called the hyponitrites or nitrites. 



LECTURE XL VII. 

Compounds of Nitrogen and Oxygen. — Nitrous 
Acid. — Preparation and Properties. — Changes of 
Color by Heat. — Organic Compounds with Nitrous 
Acid. 

Nitric Acid. — Its Discovery. — Sources in Nature. — 
Artificial Sources. — Preparation and Properties. — 
Anhydrous Nitric Acid. — Purification, Tests for. — 

. Its Salts. 

Nitrous Acid. N0 4: =4:6. 
This acid is also called hyponitric acid and peroxide 
of nitrogen. It may be made from the union of one 
volume of dry oxygen with two of dry deutoxide of ni- 
trogen, the mixture being cooled to 20°. It also arises 
in the earthen-ware cup of Grove's battery from the de- 
oxidation of nitric acid. It is most conveniently pre- 
pared by distilling in a retort, a, Pig. 243, dry nitrate 
of lead at a high temperature, and receiving the product 
into a tube, 5, artificially cooled by a freezing mixture, c. 

How may hyponitrous acid be made? What are its properties? 
What is the action of water on it ? How may nitrous acid be made ? 



262 PKOPERTIES OF NITROUS ACID. 

Fig 243 ^ ne n ^rous acid condenses as a 

a colorless liquid, which becomes 

,/^p^vg. r yellow as the temperature rises. 

Cbf ^u^ZHII^ ^ ts s P ec ifi c gravity is 1.45. It 
Jj£ (iJjj^^^Tl crystallizes at 16°, and boils at 82°. 

C=r) C |§|___^3 It can only be preserved in her- 
^-~^ metically- sealed tubes. The va- 

por is interesting optically ; when its temperature is low 
it is colorless, at 32° it is pale yellow, at 60° deep orange, 
and finally becomes by farther heating almost black. If 
the gas be examined by the aid of a prism or spectro- 
scope, a great number of lines are found in the spectrum 
of light that has passed through it (page 98). As the 
temperature "is caused to rise, these increase in breadth 
and number to such an extent that eventually no light 
at all can pass. 

Nitrous acid gas, when once mixed with atmospheric 
air, can with difficulty be condensed into the liquid form. 
It is irrespirable and of a suffocating odor. Nitrous 
acid is decomposed by water, 

3ArOt=2jsrOs+Jsro 2 , 

nitric acid and deutoxide of nitrogen arising at higher 
temperatures, while at lower ones nitric and hyponitrous 
acids are formed, 2JV0 4 =JST0 5 +N'0 3 . 
The vapor of nitrous acid is absorbed by nitric acid, 
communicating to it colors which vary with the specific 
gravity of the nitric acid. At 1.5 it is deep orange, at 
1.4 yellow, at 1.3 greenish blue, at 1.15 colorless. 

Though nitrous acid does not combine without de- 
composition with alkaline bases, it forms some remark- 
able combinations with organic bases. Pyroxyline, or 
gun-cotton of the explosive variety, contains 5 equiva- 
lents of this acid, photographic pyroxyline 4 equivalents. 
That having 3 equivalents of nitrous acid forms an opal- 
ine collodion when dissolved in ether and alcohol ; that 
with 2 equivalents is soluble in water. 

Nitrous acid is a powerful oxidizer, sulphur, phos- 
phorus, and the metals decomposing it with the evolu- 
tion of nitrogen. 

What are its properties ? How does the color of its vapor change 
by heat ? What is seen on examining the spectrum of light passed 
through it? What is the effect of water on nitrous acid? What 
are the compounds of nitrous acid with organic bases? 



NITRIC ACID. 263 

Nitric Acid. 2FO b —b4:. 

Nitric acid was discovered in the ninth century by 
the alchemists. Until the discovery of this and some 
of the other powerful acids, chemistry can hardly be 
said to have existed. The Egyptians, Greeks, and Ro- 
mans had no acid stronger than vinegar. The consti- 
tution of nitric acid was determined synthetically by 
Cavendish. He formed it by passing electric sparks 
through a mixture of 7 volumes of oxygen and 3 of ni- 
trogen, in contact with a solution of potassa. Nitrate 
of potassa was obtained. 

Nitric acid exists to a small extent in rain-water, and 
in this case either arises from the effect of the electric 
flashes upon the atmosphere, or from the oxidation of 
ammonia in the air. The nitrates of potassa and soda 
exist naturally in the East Indies and in North and 
South America. They may be formed artificially by the 
oxidation or decay of organic matter in contact with 
basic bodies. In this way the nitre used for gunpowder 
is produced on a large scale in Europe. 

In most of these cases the nitric acid arises from the 
oxidation of ammonia produced during putrefaction. 
' b J^JI 3 +0 8 =JSr0 5 +sirO. 

Common nitric acid is made by distilling equal weights 
of nitrate of potassa or soda and sulphuric acid. On the 
large scale the process is conducted in iron vessels, but 
in the laboratory glass vessels are used. 

If a less quantity of sulphuric acid be employed, the 
nitric acid is of an orange color, from the presence of 
nitrous acid ; and, in addition, the soluble bisulphate of 
potassa is not formed, but a sparingly soluble sulphate, 
and the retort may be lost. The decomposition is as 
follows : 

ko, Jsro 5 +2{na, so 3 )=jb:o, no, 2So 3 +no,$ro 5 . 

The hydrated nitric acid thus produced is a colorless 
liquid, which boils at 247° if its specific gravity be 1.42, 
the boiling point being higher if the proportion of wa- 
ter be larger. It freezes at —40°, but, when diluted with 
half its bulk of water, at —2°. It is decomposed into 

When was nitric acid discovered? How did Cavendish form it? 
Why does nitric acid exist in rain-water ? From what sources is ni- 
trate of potassa produced? How may nitric acid arise from ammo- 
nia ? How may nitric acid be made ? What are its properties ? 




264 PROPERTIES OF NITRIC ACID. 

oxygen and nitrogen by passage through a white-hot 
tube ; at a lower temperature, nitrous acid, water, and 
oxygen arise. In the light it suffers decomposition and 
turns yellow, on account of the nitrous acid which dis- 
solves in it ; it may be freed from that acid by boiling 
in a glass vessel. From its property of tinging animal 
substances yellow, it is useful in dyeing. Its action on 
many metals and combustible bodies is very violent, 
from its great oxidizing powers. Poured on phosphorus 
it produces an explosion. If some pieces of iron are 
Fig. 2u. placed in a glass under a bell-jar, Fig. 244, the 
vapors of nitrous acid are given off with ef- 
fervescence. It is often necessary to add a 
little water to start the action. Ignited char- 
coal thrown upon strong nitric acid burns 
vigorously. 

Nitric acid was, until 1840, regarded as a 
hypothetical body, the strongest aqua fortis 
of a specific gravity of 1.52 containing one equivalent 
of water. Its formula is therefore 
NO b +HO, 
though its moleoular constitution is regarded as being 
B, NO,. 
The anhydrous acid is formed by the action of chlorine 
on dry nitrate of silver, heated in a tube at first to 300°, 
and eventually to 150°. It crystallizes in colorless rhom- 
bic prisms, which fuse at 85°, and boil with decomposi- 
tion at 113°. The solution of these crystals in water 
causes a rise in temperature, and they then gain the acid 
properties which they did not possess in the solid state. 
Nitric acid may be purified by distillation, the first 
parts which come over containing chlorine and nitrous 
acid, and the last parts, containing sulphuric acid, being 
rejected. 

This acid may be detected by the addition of sulphur- 
ic acid and a crystal of protosulphate of iron, a brown 
color being produced ; or by its action on copper filings, 
with the evolution of red fumes. On boiling a nitrate 
with hydrochloric acid and a piece of gold leaf, the gold 

On passing through a heated tube, what happens to it? Why is 
nitric acid yellow? What is its action on the skin and metallic 
bodies? How may anhydrous nitric acid be made? How may ni- 
tric acid be purified ? How may it be detected ? 



SULPHUR. 265 

is dissolved, forming a yellow solution. The gold will 
be precipitated as a purple powder by protochloride of 
tin. 

The nitrates deflagrate when burned with combusti- 
ble matter, as may be shown by igniting a mixture of 
nitre and sugar. From the solubility of all its salts, 
nitric acid can not be determined by precipitation. The 
salts are mostly neutral, though some of the metallic 
ones are basic. 



LECTURE XL VIII. 

Sulphur. — Sources in Nature. — Its Three Forms. — 
Properties of Sulphur. — Its Vapor. — Oxygen Com- 
pounds. 

,Sulphurous Acid. — Preparation and Properties. — Col- 
lection by Displacement. — Bleaching Powers. — liq- 
uefaction. — The Sidphites. 

Sulphur. $—16. 

The sulphur of commerce is derived either from vol- 
canic regions or from the distillation of metallic sulph- 
ides. Iron pyrites contains 54 per cent, of sulphur, con- 
taminated, however, with arsenic. It also exists large- 
ly in the sulphates of lime, baryta, etc., and in many or- 
ganic substances. 

It is found in three forms in commerce — roll sulphur, 
flowers of sulphur, and milk of sulphur. The first re- 
ceives its name from being cast into cylindrical moulds; 
the second is derived from the first by sublimation ; the 
third is obtained by precipitation from the tersulphide 
of potassium or protosulphide of calcium with hydro- 
chloric acid. 

Sulphur commonly exists as a solid of a yellow color, 
and of a specific gravity of 1.99, having no taste, but a 
peculiar odor. It volatilizes at 180°, and melts at 226° 
into a yellow liquid. If the temperature be raised to 
about 450° it changes to a dark brown color, and be- 
comes so viscid that the vessel may be turned upside 

When do the nitrates deflagrate ?mff nder what forms does sul- 
phur naturally occur ? What arc itscommercial forms ? Describe 
the properties of sulphur. 

M 



266 SULPHUR. 

down without the sulphur flowing out. At about 800°, 
if out of contact w T ith the air, it boils, producing an am- 
ber-colored vapor. If cooled in water after having been 
melted at a low temperature, it solidifies into ordinary 
sulphur; but if heated to near 600° and then suddenly 
cooled, it becomes elastic like India-rubber, and may be 
drawn into threads. In this state it may be used for 
taking casts of coins, etc., because it slowly returns to 
the hard state. Sulphur presents six different allotropic 
conditions, in the form of black sulphur being insoluble 
in bisulphide of carbon, which dissolves the other vari- 
eties. 

When rubbed on flannel it becomes highly electrical, 
assuming the negative state. It was formerly used for 
electrical machines, before the powers of glass were dis- 
covered. A roll of it held in the hand crackles, the 
crystals separating from one another. It is a bad con- 
ductor of heat and electricity, and crystallizes under two 
different forms; it is therefore dimorphous. One of 
the forms is an acute rhombic octahedron, the other an 
oblique rhombic prism. When heated to 560° in the 
open air it takes fire, burning with a blue flame, and 
gives off a suffocating odor, that of sulphurous acid gas. 
It is wholly insoluble in water, and but slightly in alco- 
hol, ether, and chloroform. One hundred parts of bi- 
sulphide of carbon will dissolve seventy -three parts 
when warmed. 

The vapor of sulphur has the high specific gravity of 
6.64. One hundred cubic inches, at the ordinary temper- 
ature and pressure, would theoretically weigh 205.44 
grains. In it metallic bodies burn like in oxygen gas. 
Fig. 245. If a gun-barrel containing a 

piece of sulphur, and closed 
at the muzzle, be heated red- 
hot, the ignited jet of sul- 
phur vapor issuing from the 
touch-hole will cause a bunch 
of iron wire to take fire and 
burn brilliantly, Fig. 245. A very important applica- 

What changes occur in itduring melting ? What electrical con- 
dition does it assume? WlflBps its conducting power? Why is it 
called dimorphous? What is produced by its combustion? What 
phenomenon is shown by its ignited vapor ? 




COMPOUNDS OF SULPHUR. 267 

tion, in the arts, of sulphur, is made in the process call- 
ed vulcanization, which consists in dipping India-rubber 
in melted sulphur, and then subjecting it to a tempera- 
ture of about 300°. The rubber retains about two per 
cent, of sulphur, and gains the property of resisting its 
usual solvents, and of retaining perfect plasticity and 
pliancy through a range of many degrees. Silicate of 
magnesia is often mixed with the rubber, to give a 
smooth surface. The sulphides may be used instead 
of sulphur. 

Sulphur has a very great range of affinities, combining 
with most metallic substances in several different pro- 
portions, with hydrogen, and with oxygen. With the 
latter it furnishes seven compounds : 

50 2 , Sulphurous Acid. 

50 3 , Sulphuric Acid. 

S 2 2 , Hyposulphurous or Dithionous Acid. 

S 2 5 , Hyposulphuric or Dithionic Acid. 

S 3 O s , Trithionic Acid, or Acid of Langlois. 

/S 4 6 , Tetrathionic Acid, or Acid of Fordos and Gelis. 

S 5 O b , Pentathionic Acid. 

Of these, the first three are the most important. 

Sulphurous Acid. S0 2 —o2. 

This acid may be formed by burning sulphur in oxy- 
gen or in air ; in the latter case the gas is mixed with 
nitrogen. The combustion may be conducted under a 
bell-jar, the sulphur being placed on a stand. A better 
process is to partially deoxidize sulphuric acid by heat- 
ing it with mercury, an oxide of mercury forming, which 
is converted into a sulphate by the excess of sulphuric 
acid. It may also be produced by the action of sulphur- 
ic acid on charcoal, copper filings, or sulphur. A mix- 
ture of three parts of black oxide of manganese and one 
of sulphur yields it. It must be collected either over 
mercury or by displacement, unless a solution in water 
is wanted. 

Sulphurous acid is usually a transparent colorless gas, 
of a sour taste, and suffocating, sulphurous odor. It is 

Of what use is sulphur in the arts? What are the oxygen com- 
pounds of sulphur? How may sulphurous acid be made? What 
other processes are there for its manufacture ? What are the prop- 
erties of sulphurous acid ? 



268 



SULPHUROUS ACID. 




entirely irrespirable, and extinguishes flame at once, be- 
ing for this reason employed to put out fires in chim- 
neys, a handful of sulphur being burnt at the bottom of 
the flue. Its specific gravity is 2.2112 ; one hundred cu- 
bic inches weigh 68.48 grains. If a stream of it, which 
Fig. 246. has been cooled by flowing 

from the generating flask, a, 
Fig. 246, through a bent tube, 
#, immersed in cold water, be 
carried to the bottom of a 
jar, c, the gas will displace 
the atmospheric air, floating it 
out of the vessel. This pro- 
cess, called the method of dis- 
placement, is useful in collecting gases soluble in water. 
A taper put in a jar of sulphurous acid gas is extin- 
guished at once. If the jar be inverted over water, the 
gas rapidly dissolves, the liquid taking up about fifty 
times its volume. Alcohol absorbs 115 volumes. Veg- 
etable colors submitted to it are bleached, but not per- 
manently, as in the case of chlorine, where the coloring 
matter is destroyed, its hydrogen going to form hydro- 
chloric acid. The colors may be restored by an acid or 
alkali. Sulphurous acid will support the combustion of 
potassium or sodium vividly. 

This acid gas very readily takes the liquid form if it 
be cooled by a freezing mixture to 14°. It has then a 
specific gravity of 1.45, and evaporates so quickly as to 
produce a very intense cold, by which mercury may be 
frozen, or water congealed in a red-hot capsule. Sul- 
phurous acid suffers no change at a red heat unless hy- 
■ drogen be present, when water is formed and sulphur 
deposited. Oxygen, in presence of water, slowly turns 
it into sulphuric acid. 

Sulphurous acid forms with bases a series of salts — 
the sulphites. They are easily decomposed by chlorine, 
nitric acid, and other oxidizing agents, passing into the 
condition of sulphates ; they can also reduce the metal- 
lic oxides. 

What is the method of displacement? What is its solubility? 
How does its bleaching power compare with that of chlorine ? How 
may it be condensed? What are the properties of this liquid? 
What salts does sulphurous acid form ? 



SULPHURIC ACID. 269 



LECTURE XLIX. 

Compounds of Sulphur and Oxygen. 

Sulphuric Acid. — Anhydrous Sulphuric Acid. — Its 
Properties. — Nordhausen Oil of Vitriol. — Its Prepa- 
ration and Constitution. — Common Sulphuric Acid. 
— Method of Preparation. — Properties. — Impurities. 
— Tests for. 

Hyposidphurous Acid. — Hyposulphite of Soda. 

Sulphuric Acid. SO 3 = 4:0. 

This compound is the most important of all acids. 
By its aid nitric, hydrochloric, and many other acids are 
prepared. It is also largely consumed in the prepara- 
tion of carbonate of soda from, sea-salt, and of chloride 
of lime. 

There are several varieties of sulphuric acid, differing 
from one another in the amount of water that they con- 
tain. 1st. There is anhydrous sulphuric acid, or sul- 
phuric anhydride (S0 3 ), which is prepared by heating 
Nordhausen oil of vitriol to 290°, when a white crystal- 
line substance like asbestos distills over. It fumes in the 
air, melts at 66°, and boils at 110°. It has an intense af- 
finity for water, hissing like a hot iron when placed in 
it. The acid properties of this substance are very slight; 
it shows but little tendency for combination, and does 
not form true sulphates. 

2d. Saxon or Nordhausen oil of vitriol, S0 3 -\-S0 3 , 
HO, is prepared by distilling protosulphate of iron (green 
vitriol) which has been exposed to a heat sufficient to 
remove its seven atoms of water. If this dry powder 
be placed in a retort and exposed to a high temperature, 
there distills over an oily liquid, hence called oil of vit- 
riol. It is a dihydrate — that is, contains two atoms of 
acid and one of water. It completely dissolves sulphate 
of indigo. 

3d. Common sulphuric acid, S0 3 , HO, called commer- 

What is the formula of sulphuric acid ? What varieties of sul- 
phuric acid are there? How is the anhydrous acid made? What 
is the process for making Nordhausen oil of vitriol ? What is its 
composition ? How is commercial sulphuric acid made ? 



270 SULPHURIC ACID. 

cially oil of vitriol. It is made by burning sulphur or 
pyrites in a regulated current of air, and conducting the 
sulphurous acid into chambers lined with lead, into which 
steam and nitrous acid, produced from the action of sul- 
phuric acid on nitre, are admitted. The sulphurous acid 
takes oxygen from the nitrous acid, reducing it to deut- 
oxide of nitrogen ; but that, in turn, takes oxygen from 
the atmospheric air that is present, and becomes again 
nitrous acid. The deutoxide acts as an oxygen carrier. 
The bottom of the chamber, being covered with water, 
becomes gradually saturated with sulphuric acid, when 
it is drawn off and corrcentrated in leaden and then pla- 
tinum boilers. Its specific gravity is eventually 1.845. 
It is a dense oily liquid, freezing at —30°, and boiling 
at 650°. Sulphuric acid of a specific gravity 1.78 freezes 
at 40° in large crystals. 

The affinity of sulphuric acid for water is very intense. 
Fig. 24T. If a tube, #, containing sulphuric ether, be stir- 
red in a glass, a, Fig. 247, in which a mixture 
of sulphuric acid 3 parts, and water 1 part, has 
been made, the temperature will rise to 300°, 
and the ether boil. On the same principle, it 
is useful for removing water from gases, unci, 
as is shown in Lecture XII., that liquid may be 
frozen on account of the rapidity with which sulphuric 
acid absorbs its vapor. Organic substances are charred 
by the action of this acid, which removes the constitu- 
ent water, and sets the carbon free. 

Sulphuric acid is not found pure in commerce, con- 
taining sulphate of lead, derived from the lining of the 
chambers in which it is made, and frequently arsenic, 
selenium, tin, and nitrous acid. The dark color it pre- 
sents is due to carbonaceous matter. The acid is tested 
for by chloride of barium or nitrate of baryta, the white 
sulphate of baryta being insoluble in water or acids. It 
reddens black woolen materials, but the stain is removed 
by ammonia. 

In addition to the above hydrates of sulphuric acid, 
there are two others : 

4. Bihydrate, S0 3 , 2HO, boils at 435°, specific gravity 1.78. 

5. Terhydrate, S0 3 , 3HO, " 348°, " " 1.63. 

What are the properties of sulphuric acid ? How may its affinity 
for water be shown? What are its usual impurities? How is it 
detected ? 




HYPOSULPHUROUS ACID. 271 

Hyposulphurous Acid. S 2 2 . 

This acid is only known in the combined state. On 
attempting to separate it from its salts, it decomposes 
into sulphur and sulphurous acid, 

S 2 2 =S+80 2 . 
The hyposulphite of soda is of great use in photographic 
operations, from its power of dissolving the compounds 
of silver. If any trace of the salt is left in a paper proof, 
it will eventually cause it to become yellow and fade 
away. 

The other compounds of sulphur and oxygen possess 
but little interest. 



LECTURE L. 

Sulphur and Phosphorus. — Sulphureted Hydrogen. 
— Preparation and Properties. — Uses as a Test. — 
Sulphur Waters. — Persulphide of Hydrogen. 

Selenium. 

Phosphorus. — Made from Bone-earth. — Properties. — 
Shines in the Dark. — Inflammability. — Allotropic 
Phosphorus. — Compounds with Oxygen. 

Sulphureted Hydrogen. HS—ll. 
This gas may be prepared by the action Fig. us. 
of hydrochloric acid on sulphide of anti- 
mony, in the apparatus Fig. 248, or of di- 
lute sulphuric acid on sulphide of iron. It 
must be collected over either warm or salt 
water. If made by sulphide of iron, the 
action is as follows : 

m FeS+S0 3 , HO=HS±FeO, S0 3 . 
It is called also hydrosulphuric acid and 
sulphydric acid. 
- Sulphureted hydrogen is a colorless gas, having ar 
fetid odor like rotten eggs. It is so diffusible that a 
very small quantity will taint the air of a large room. 
It is absorbed by water, that fluid taking up three times 

What are the uses of hyposulphurous acid ? How may sulphuret- 
ed hydrogen be prepared ? What are its properties ? 




272 



SV/LPHURETED HYDROGEN. 



Fig. 240, 



its volume at 60°. In this form it is rapidly decomposed 
by the contact of air, the hydrogen forming water with 

the oxygen, and the sul- 
phur depositing. The spe- 
cific gravity of sulphureted 
hydrogen gas is 1.1747; 
one hundred cubic inches 
weigh 36.38 grains. It is 
inflammable, and may be 
burnt from a jet, as in Fig. 
249. If the access of air 
is unlimited, sulphurous 
acid and water arise; if 
limited, water is produced 
and sulphur deposited. It 
reddens litmus slightly, 
and combines with met- 
als to form sulphides. For 
this latter reason it is very 
valuable in analytical op- 
erations, many of the sul- 
phides being insoluble and 
highly colored : antimo- 
ny gives an orange .pre- 
cipitate, arsenic a yellow, 
lead a brown, manganese 
a flesh-colored. It tarnishes silver, the metal passing 
through various shades of yellow and orange to black- 
ness. It is liquefied by a pressure of 17 atmospheres 
at 50°, the specific gravity being 0.9. When cooled to 
— 122° it solidifies into a white substance. 

The action of sulphureted hydrogen is illustrated by 
writing on a sheet of paper with a solution of acetate 
of lead. The letters are invisible until exj)osed to a cur- 
rent of the gas, when they become black. 

Sulphureted hydrogen is a natural constituent of some 
mineral waters, as at Sharon, in New York, and at the 
Virginia Sulphur Springs. It is also found in the air of 
sewers and in putrefying animal matter, and has been 
supposed to be the cause of miasmatic fevers. It is 

What is its solubility ? What arises from its combustion ? What 
precipitates does it give with metallic oxides ? At what points does 
it liquefy and solidify? Does it exist naturally?. 




PHOSPHORUS. 273 

very poisonous when respired, even when dilute, causing 
nausea, headache, and faintness. 

There is another compound of sulphur and hydrogen, 
the persulphide of hydrogen, the composition of which 
is supposed to be HS 5 . It is a heavy yellow liquid, of 
a specific gravity 1.76. 

Selenium. #6 =40. 
This substance is found in certain varieties of iron 
pyrites. It resembles sulphur in many respects, and has 
a reddish-brown color and dim metallic lustre. It tinges 
flame of a light blue color, and gives off an offensive 
odor. With oxygen it forms three compounds : 

SeO, Oxide of Selenium. 
Se0 2 , Selenious Acid. 
SeO s , Selenic Acid. 

With hydrogen it unites to form seleniureted hydrogen. 

Phosphorus. P=32. 

This substance, so named from shining in the dark, 
was discovered in 1669 by Brandt. It is now produced 
from phosphate of lime or bone-earth, but is also found 
in other animal matters, more particularly in the brain 
and nervous tissue. 

The process for production is to burn the bones, grind 
them, and digest them in dilute sulphuric acid for six 
hours, steam being passed into the mixture to hasten 
the changes. The liquid is then strained, evaporated to 
dryness, fused, and mixed with one fourth of its weight 
of charcoal. It must then be distilled at a white heat 
in a stone-ware retort, the neck of which dips beneath 
warm water. A part of the phosphoric acid is deox- 
idized by the charcoal, carbonic oxide escaping and 
phosphorus coming over. It is purified by melting and 
straining through chamois leather. In Great Britain 
about six tons are annually used in the manufacture of 
matches, one pound making 600,000 matches. 

Phosphorus is tasteless, transparent, and colorless. 

What are its relations to respiration ? What other compound of 
sulphur and hydrogen is there ? Describe selenium. From what is 
phosphorus derived ? Describe the process for its production. To 
what use is phosphorus applied in the arts? What are its proper- 
ties ? 

M2 



274 PROPERTIES OP PHOSPHORUS. 

Exposed to light it turns reel, even in a vacuum, owing 
to undergoing a molecular change. In general appear- 
ance it resembles wax. In 'the air it slowly oxidizes, 
smoking, and exhaling an electrical odor. At 32° it is 
brittle; at 110°. it melts; at 570° it boils in close ves- 
sels. In the air it takes fire at 120°, burning with the 
evolution of anhydrous phosphoric acid. Its specific 
gravity is 1.826. Phosphorus is so poisonous that a 
few grains will destroy life, and those engaged in the 
manufacture of matches frequently suffer from necrosis 
of the louver jaw-bone. 

Phosphorus requires to be kept under water in order 
to avoid oxidation, and must also be handled carefully. 
A few pieces placed between brown paper and rubbed 
take fire, and it will also inflame if sprinkled with lamp- 
black or powdered animal charcoal. Placed on dry 
wood, flannel, feathers, or other non-conducting sub- 
stances, It will ignite, if in thin slices. In chlorine, or 
the vapor of Jbromine or iodine, it burns spontaneously. 

If phosphorus is suddenly cooled from the fused con- 
dition it undergoes a change, becoming passive. This 
allotropic modification may also be produced by distill- 
ing it in an atmosphere of nitrogen or carbonic acid. 
For the purposes of commerce it is prepared by keeping 
phosphorus heated to 450° for three or four weeks in 
an air-tight iron vessel. It may then present a black, 
gray, or scarlet color, and will not take fire under a 
temperature of 500°. It is insoluble in bisulphide of 
carbon, does not shine in the dark, shows no disposition 
to unite with sulphur, and will not oxidize in the air. 

Phosphorus and oxygen form four compounds : 

P 2 0, Oxide of Phosphorus. 
PO, Hypophosphorous Acid. 
-P0 3 , Phosphorous Acid. 
-P0 5 , Phosphoric Acid. 

Is phosphorus poisonous? Give examples of its combustibility. 
How may passive phosphorus be made? How many compounds of 
phosphorus and oxygen are there? 



OXYGEN COMPOUNDS OF PHOSPHORUS. 275 



LECTURE LI. 

Compounds of Phosphorus and Oxygen. — Oxide 
of Phosphorus, Preparation of, — Hypophosphorous 
and Phosphorous Acids. — Phosphoric Acid. — Prep- 
aration. — Compounds with Water. — Properties of 
these Acids and their Salts. — Phosphureted Hydro- 
gen. — Three Compounds of Phosphorus and Oxy- 
gen. — Spontaneous Inflammability of Phosphureted 
Hydrogen. — Chlorine. — Existence in Nature. — 
Preparation. — Liquefaction. — Relations to Combus- 
tion and Respiration, 

Oxide of Phosphorus. P 2 0. 

When phosphorus is burned in air, the red residue 
is this body. It may be formed in quan- Fig. 250. 

tity by passing a stream of oxygen from ^ ^^ffr 

the tube a, Fig. 250, upon phosphorus 
under hot water in a glass, b. A brill- 
iant combustio'h takes place, phosphoric 
acid and the oxide resulting. The for- 
mer is dissolved by the water, and the 
latter, when washed with bisulphide of 
carbon, is left in a state of purity, 

Hypophosphorous Acid, jPO, 

is prepared by acting on phosphide of barium with wa- 
ter, and treating the solution with sulphuric acid as 
long as any precipitate falls. £t is a powerful deoxidiz- 
ing agent. Some of the hypophosphites are useful in 
medicine. 

Phosphorous Acid, P0 3 , 

is formed by the combustion of phosphorus in a limited 
amount of dry air. It is then seen as a dry white pow- 
der. It may be obtained in solution by setting a num- 
ber of sticks of phosphorus, inclosed in glass tubes, 
around a fu nnel placed in the neck of a bottle. It has 

How is oxide of phosphorus made ? How are hypophosphorous 

and phosphorous acids made ? 




276 PHOSPHOEIC ACID. 

powerful deoxidizing properties, taking the oxygen from 
sulphuric acid, and causing it to deposit sulphur. 

Phosphoric Acid. JP0 5 . 

The anhydrous form originates when phosphorus is 
mg. 251. burned in dry air or oxygen, Fig. 251. 
It- condenses in white snowy flakes, 
which hiss like hot metal when dipped 
in water. It may be made by the action 
of nitric acid on phosphorus. It is very 
deliquescent, and scarcely shows any acid 

I properties before uniting with water. It 

m | may be detected by its yellow precipitate 




*^ with molybdate of ammonia. 
Phosphoric acid unites with water in three propor- 
tions, producing 

Monobasic Phosphoric Acid . . . PO& HO 
Bibasic " " . . . PO s , 2HO 

Tribasic " " . . . jP0 5 , SHO 

These also have been called metaphosphoric, pyro- 
phosphoric, and common phosphoric acids. 

The first, the protohydrate of phosphoric acid, is pro- 
duced when any of the watery solutions of phosphoric 
acid are evaporated to dryness, a body called glacial 
phosphoric acid resulting. It gives a white granular 
precipitate w T ith nitrate of silver, and coagulates albu- 
men. Its salts contain one atom of base to one of acid. 
By boiling with water it goes into the tribasic form. 

The second, the bihydrate of phosphoric acid, can be 
made by heating common phosphoric acid to 417° for 
some time. It neither precipitates silver nor coagulates 
albumen, though its salt^ield w r ith silver a flaky pre- 
cipitate. It also turns to tribasic acid by boiling with 
water. 

The third, the terhydrate of phosphoric acid, may be 
obtained from phosphate of lime by the action of sul- 
phuric acid, sulphate of lime being formed, or by boil- 
ing anhydrous phosphoric acid in water. It neither 
precipitates silver nor coagulates albumen, but its salts 
give canary-yellow precipitates with nitrate of silver. 

How is anhydrous phosphoric acid made ? What compounds 
does it yield with water ? How is the protohydrate produced ? How 
are the bihydrate and terhydrate made ? What are their properties ? 



PHOSPHUEETED HYDROGEN. 



277 



These hydrogen acids of phosphorus give rise to a 
very complex series of salts, according to the extent to 
which the hydrogen is replaced by metallic bodies. 
The monobasic acid can only yield one class of salts, in 
which all its hydrogen is replaced by a metal ; but the 
bibasic can yield two series, according as the metal re- 
places one or both atoms of base ; the tribasic can yield 
three series, according as one, or two, or three of the 
hydrogen atoms are displaced. 

Phosphueeted Hydeogen. JPIf 3 z=35. 

Phosphorus forms three compounds with hydrogen : 
a gas, JPH 3 ; a liquid, PH 2 ; and a solid, P 2 H. The first 
is best known, and is made by boiling phosphorus in a 
strong solution of potassa in a retort, Fig. 252, the neck 

Fig. 252. 




of which dips beneath the surface of water. As the 
bubbles of gas break on the water they take fire, burn- 
ing with a bright yellow light, and there ascends 
through the air a ring of smoke, which dilates as it 
rises, and exhibits a rotating motion in its parts. The 
gas may also be made by putting phosphuret of calcium 
in water. 

Phosphureted hydrogen is a colorless gas, having a 
smell like garlic or putrid fish. Water takes up one 
eighth its volume. The spontaneous combustibility 

results from an admixture of the vapor of the liquid 

— ^ 

How many series of salts can each class yield? Describe the 
preparation of phosphureted hydrogen. What are its properties? 



278 



CHLORINE. 



phosphuret ; phosphoric acid and water arise. Its spe- 
cific gravity is 1.185. 

Phosphorus forms also compounds with nitrogen, 
chlorine, bromine, iodine, and sulphur. 

Chlorine. Cl=?35.5. 

Chlorine was discovered by Scheele in 1774, and was 
originally called oxymuriatic acid. It derives its name 
from its greenish color. It is not found free in nature, 
but exists in abundance in common salt, the chloride of 
sodium, a material which gives salinity to the ocean. 

Chlorine may be obtained by the action of sulphuric 
acid on common salt and black oxide of manganese, 
or better by heating a mixture of hydrochloric acid and 
black oxide of manganese. The action in the latter case 
is as follows : 

Mn 2 + 2JBTCl= Mn Cl+ 2HO+ 01 
One atom of peroxide of manganese and two of hydro- 
chloric acid give one atom of chloride of manganese, 
two of water, and one of chlorine. Half the chlorine is 
given off as gas, and half remains in combination. 

The apparatus for its production is seen in Fig* 253, 



Fin. 253. 




where a is the retort, with the generating materials, 
connected with a small receiver, 5, to retain part of the 
water which the gas may bring over; this, again, is 
connected with a chloride of calcium tube, e, which ef- 

When was chlorine discovered? In what substances does it oc- 
cur ? How may it be formed? Describe the apparatus for its pro- 
duction. 



PROPERTIES OF CHLORINE. 2*79 

fects the perfect drying of the gas. As chlorine is very 
soluble in cold water and acts on mercury, it can nei- 
ther be collected at the pneumatic nor mercurial trough. 
It may, however, be gathered over warm water, or a 
saturated solution of common salt, or by displacement. 

Chlorine is a greenish-yellow gas that may be lique- 
fied by a pressure of four atmospheres, or by cooling to 
•—106° ; it has not been solidified. It forms with water 
a crystalline hydrate, having the composition Cl+lOJIO. 
On inclosing these crystals in a bent tube and heating 
them, the resulting chlorine will be liquefied by its own 
pressure. 

A taper immersed in chlorine burns for a short time, 
emitting volumes of black smoke, Fig, 254, 2^.254. 
which are due to the fact that the hydrogen 
of the fatty compound is alone uniting with 
the gas to produce hydrochloric acid, while 
the carbon, which has but slight affinity for 
chlorine, is set free. Powdered antimony or 
brass leaf immersed in this gas becomes in- 
candescent, and consumes, a chloride result- 
ing. Phosphorus takes fire in it at ordinary 
temperatures, and burns with a pale flame. The odor 
of chlorine is pungent, and, even when dilute, irritating 
to the mucous membrane of the air passages, producing 
a hoarseness which may last several days. Mixed with 
aqueous vapor and very much weakened, it is said to be 
of advantage in pulmonary complaints. 

What are its properties? What is its action on a burning taper ? 
How does it act on certain metals and phosphorus ? What is its 
effect on the animal system ? Which is the most valuable property 
of chlorine ? 




280 PROPERTIES OF CHLORINE. 



LECTURE LII. 

Chlorine, continued. — Bleaching and Disinfecting 
Powers. — Combustion of Hydrocarbons. — Tests for 
Chlorine. — Chlorine Water. — Oxygen Compounds. 
— Hypochlorous, Chlorous, Hypochloric, Chloric, and 
Perchloric Acids. — Bleaching with Chloride of Lime. 
— Chloride of Nitrogen an explosive Compound. — 
Hydrochloric Acid. — Preparation in the Gaseous 
and Liquid Conditions. 

The bleaching properties of chlorine render it of the 
greatest value in the arts. Previous to its introduction, 
woven fabrics, for example, were bleached by exposure 
to the sunshine and moisture, a process demanding a 
length of time and a large open space. The same oper- 
ation can now be performed in a few hours in a con- 
fined apartment. This property may be illus- 
trated by pouring a solution of litmus or indigo 
through a funnel, a, into a flask, b, containing 
chlorine, Fig. 255. The decoloration takes place 
at once. A solution of chlorine in water may 
also be used. Chlorine is employed by physicians 
for disinfecting the air of foul rooms, as those in 
which hospital gangrene has been prevalent. 
Such effluvia contain hydrogen,. which unites with the 
chlorine, and the noxious compound is decomposed. 
Some have supposed these properties to be due to the 
evolution of nascent oxygen. It should be disengaged 
Fia. 256. s l°wiy? if patients are in the room, by the ac- 
tion of dilute sulphuric acid on chloride of lime. 
The peculiarities of chlorine as a supporter of 
combustion are well seen when a piece of blot- 
ting-paper, Fig. 256, saturated with turpentine, 
is placed in ajar of the gas. It takes fire with 
the evolution of clouds of carbon smoke. This 
phenomenon depends on the intense affinity 
that chlorine has for the electro-positive bod- 

What is the most valuable property of chlorine ? How may it be 
illustrated ? How does it act on effluvia ? What is the cause of 
the smoke when hydrocarbons are burned in chlorine ? 





PROPERTIES OF CHLORINE. 281 

ies, though it unites with carbon with reluctance. A 
green wax taper, the wick of which carries a spark, 
will rekindle in chlorine, and continue to burn. 

Free chlorine may be detected by its smell, its 
bleaching action on vegetable compounds, and its white 
curdy precipitate with nitrate of silver. This compound 
chloride of silver, which changes to a dark color in the 
light, is used for the production of photographs on pa- 
per, very large quantities being consumed in that appli- 
cation. Chlorine water is made by agitating water in 
a bottle of chlorine, the mouth of the bottle from time to 
time being opened under water. This solution decom- 
poses in the sunshine, oxygen gas being liberated and 
hydrochloric acid formed by the decomposition of the 
water. The specific gravity of chlorine is 2.487, and 
100 cubic inches weigh 77.04 grains. 

Chlorine unites with oxygen, producing 

CIO, Hypochlorous Acid. 

C10 3 , Chlorous Acid. 

ClOu Peroxide of Chlorine, Hypochlorie Acid. 

C70 5 , Chloric Acid. 

ClO : , Perchloric Acid. 

Hypochlorous Acid. 010=43.5. 

This acid is often obtained by acting on the red ox- 
ide of mercury, suspended in water, with chlorine. The 
gaseous acid is procured by placing the aqueous solution 
in a tube inverted over mercury, and passing dry ni- 
trate of lime into it. It is deeper-colored than chlorine, 
a more powerful bleaching agent, and oxidizes vigor- 
ously. The warmth of the hand causes it to explode, 
as does also the direct sunshine. Water dissolves 200 
times its volume of this gas. The specific gravity is 
3.04, and 100 cubic inches weigh 94.16 grains. 

The most common bleaching compound is the chlor- 
ide or hypochlorite of lime. The composition seems to 
be CaO, CIO + OaOl. The articles to be bleached are 
saturated with an aqueous solution of this substance, 
and then washed in dilute sulphuric acid. The quan- 

How may chlorine be detected ? How may chlorine water be 
made, and what are its properties ? Name the oxygen compounds 
of chlorine. How is hypochlorous acid made, and what are its 
properties ? What is the constitution of bleaching powder ? 



282 ACIDS OF CHLORINE. 

tity of chlorine in chloride of lime is determined by the 
process called chlorimetry. The best method is to as- 
certain how much arsenious acid, As 3 , can be raised 
to the state of arsenic acid, As0 5 , by a weighed quan- 
tity of the chloride of lime. 

Chlorous Acid. C10 3 =59.5. 

This gas is of a greenish color, and may be made by 
mixing arsenious acid with chlorate of potassa and di- 
luted nitric acid, and distilling in a water-bath. Water 
dissolves six times its volume. It explodes at 130°. 

Peroxide of -Chlorine, CT0 4 =67.5, 

is made by acting on chlorate of potassa with concen- 
trated sulphuric acid at a temperature not exceeding 
100°. It is a yellow gas, exploding at 140°, 
and soluble in water to the extent of 20 vol- 
umes. If into a glass, a, Fig. 257, contain- 
ing water, some crystals of chlorate of potas- 
sa and fragments of phosphorus are placed, 
and sulphuric acid is poured upon them 
through a long funnel, £, chlorous acid is 
liberated, and a brilliant combustion under water en- 
sues, the water becoming yellow. The gas may be 
readily liquefied ; its specific gravity is 2.33. 

Chloric Acid. CW 5 — h J5.5. 

This acid, which only exists in combination with one 
atom of water, is made by decomposing the chlorate 
of baryta by sulphuric acid, which must not be added 
in excess. This solution is to be evaporated in vacuo, 
when a sour, yellowish, sirupy liquid is produced. It 
sets on fire substances containing carbon and hydrogen, 
and has the bleaching power. One of the salts, the 
chlorate of potassa, is of use in chemistry on account 
of the facility with which it yields up oxygen. A few 
grains of this salt ground in a mortar with sulphur ex- 
plode violently. When mixed with sugar, it is in- 
flamed by a drop of sulphuric acid. 

What is chlorimetry ? How is chlorous acid made ? How is 
peroxide of chlorine made ? In what manner may phosphorus be 
burned under water ? How is chloric acid made ? What are the 
properties of chloric acid ? 




hydrochloric acid. 283 

Perchloric Acid, 670 7 = 91.5, 

is obtained by distilling perchlorate of potassa with its 
own weight of sulphuric acid, mixed with one quarter 
as much water. At 280° a dense white vapor passes 
over. It is a colorless, oily, corrosive liquid, exploding 
like chloride of nitrogen on contact with combustible 
substances, such as charcoal, ether, etc. It fumes in the 
air, and can not be kept, even in the dark, without ex- 
ploding. 

Chlorine and Nitrogen. JSTCl 3 or NCl^ 
This compound, one of the most explosive at present 
known, is formed when a solution of sal ammoniac is ex- 
posed to chlorine. A leaden basin should be placed un- 
der the jar to collect the oily liquid. Dulong lost an 
eye, and Davy was severely wounded by the explosions 
of this substance. Its specific gravity is 1.65, and it may 
be distilled at a temperature of 160°. The contact of 
oily matter causes a detonation. . 

Chlorine and Hydrogen. 
Hydrochloric Acid. HCl=:3Q.5. 
This acid, called also muriatic acid, is prepared by 
placing in a flask one part of sajf and two of sulphuric 
acid. The action may be aided by a spirit-lamp. The 
gas is conducted through a tube into a bottle contain- 
ing water. The end of the tube should dip but a short 
distance beneath the surface of the water, so that if the 
water should tend to regurgitate, it may be arrested by 
a suitable bulb, and atmospheric air allowed to pass into 
the flask. The bottle should be surrounded by ice-wa- 
ter, as a large amount of heat is extricated during the 
process of solution, and the water increases in volume 
from one to two thirds. The action is 

mCl+2{S0 3 , HO)=JICl+(JVaO, 2S0 3 , HO\\ 
that is, one atom of chloride of sodium and two of sul- 
phuric acid yield one atom of hydrochloric acid and one 
of bisulphate of soda. 

Hydrochloric acid gas may be obtained by heating 
the liquid thus obtained, and collecting it by displace- 
How is perchloric acid made, and what are its properties ? What 
are the properties of the chloride of nitrogen ? How is hydrochloric 
acid made ? How may the gas be procured ? 



284 HYDROCHLORIC ACID. 

ment. It is a transparent colorless gas, having power- 
ful acid properties, and very absorbable by water, that 
fluid taking up 500 times its volume. It fumes in moist 
air. If a dry Florence flask be filled with it by dis- 
placement, and the mouth of it then opened under wa- 
ter, the water rushes up violently, owing to the quick 
absorption of the gas. The specific gravity of the gas 
is 1.2783 ; one hundred cubic inches weigh 39.59 grains. 
It contains equal volumes of its constituents, united 
without condensation. 



LECTURE LIII. 

Chlorine continued. — Liquefaction of Hydrochloric 
Acid. — Its Production by Light. — Tlie Chlorine-Hy- 
drogen Photometer. — Action of Hydrochloric Acid 
on Metallic Oxides. — Solution of Hydrochloric Acid. 
— Its Properties. — Tests for Nitro-hydrochloric Acid. 

Iodine. — Method of Preparation. — Properties. — Re- 
actions. — Its Photographic Relations. — Hydriodic 
Acid. — Compounds of Iodine with Oxygen, Nitro- 
gen, and Chlorine. 

Hydrochloric Acij), although gaseous at ordinary 
temperatures and pressures, is liquefied by a pressure 
of forty atmospheres. At 50° it is colorless, and less 
refractive than water. 

The pure gas may be obtained by the direct union 
of chlorine and hydrogen under the influence of flame, 
the electric spark, or light. In the dark the gases do 
not combine, but if a beam of sunlight be thrown upon 
a flask containing a mixture of equal volumes, a violent 
explosion results, and the vessel is shattered to pieces. 

It was found by Dr. Draper that in this striking ex- 
periment the action is due to the chlorine, which, on ac- 
count of its color, absorbs the indigo ray, and changes 
from the passive to the active state. It. may also be 
rendered active by spongy platinum, and chlorine which 
has been exposed by itself to the sunshine unites more 

What are its properties ? How may its solubility be shown ? How 
may hydrochloric acid gas be liquefied ? What is the action of sun- 
light on a mixture of chlorine and hydrogen? To which of these 
bodies is the action due ? 



HYDROCHLORIC ACID. 285 

readily with hydrogen. Dr. Draper invented a photom- 
eter based on these phenomena (page 91), and with it 
determined many most valuable photo-chemical facts 
(Philosophical Magazine, December, 1843). 

When hydrochloric acid is brought in contact with 
metallic oxides, both are decomposed, a metallic chlor- 
ide and water resulting. 

MO+irci= MCI+ HO, 

or M 2 3 +SHCl=M 2 Cl 3 +sHO; 

that is, one atom of a metallic protoxide with one of hy- 
drochloric acid yields one of protochloride and one of 
water. In the case of a sesquioxide, one atom with 
three of hydrochloric acid gives one of metallic sesqui- 
chloride and three of water. 

The constitution of hydrochloric acid, and its ftg^m. 
action on metallic oxides, are strikingly shown 
by taking a flask, Fig. 258, filled with it, and 
pouring a fine stream of peroxide of mercury 
in through a funnel. The chloride of mercury, 
corrosive sublimate, forms at once, and drops of 
water condense on the sides of the flask. 

Liquid hydrochloric acid, or spirit of salt, as it is call- 
ed from its origin, is the most commonly used form. 
It has, when very concentrated, a specific gravity of 
1.21, boiling at 112°, and freezing at —60°. It contains 
42.4 per cent, of the acid gas. The boiling point is 
highest, 230°, when the specific gravity is 1.094, and the 
lif uid contains 20 per cent, of dry gas. The strong acid 
is weakened and the weak strengthened by boiling. 

The commercial acid is generally yellow, partly from 
chloride of iron and partly from the particles of cork 
and lute that may have fallen into it. It may also con- 
tain sulphuric acid, chlorine, sulphurous acid, tin, or ar- 
senic. From the latter it is separated by distillation 
over sulphide of barium. 

The tests for hydrochloric acid are first the dense 
white fumes of sal ammoniac, the chloride of ammo- 
nium, that it yields with free ammonia. If two bottles 
that have been rinsed out, one, c, with the acid, and the 

What is the action of hydrochloric acid on metallic oxides ? What 
is the action of hydrochloric acid on peroxide of mercury ? What 
are the properties of liquid hydrochloric acid ? What are its impu- 
rities ? What are the tests for it ? 



286 



IODINE. 






. 253. other, /i, with ammonia, are placed mouth to 
mouth, Fig. 259, they are filled with a white 
cloud very quickly. Second, with nitrate of 
silver this acid gives a curdy white precipi- 
tate of chloride of silver, which is soluble in 
ammonia. Hydrochloric acid gas is distin- 
guished from chlorine by the absence of 
bleaching power and its acid qualities, litmus 
water beins; used as the test. 



Niteo-Hydrochloric Acid 
is also called nitro- muriatic acid and aqua 
regia, and is formed by adding to hydrochlo- 
ric acid one third of its volume of nitric acid. 
It possesses the power of dissolving the no- 
ble metals, forming chlorides, a property due 
to the evolution of nascent chlorine. Nitrous 
acid and water are also set free. Heat accel- 
erates the action, but may cause the loss of some of the 
chlorine. 

Iodine. I— 126. 
This element was discovered in 1811, and is named 
from the violet color of its vapor. It is made from kelp, 
which is the ash produced by the burning of sea-weed, 
but is also found in some saline springs, in certain Mex- 
ican silver ores. 

It may be obtained by lixiviating kelp, and evapora- 
ting till no more crystals are produced. The mother- 
liquor is then treated with sulphuric acid, and subse- 
quently heated with peroxide of manganese in a leaden 
retort, a b c, Fig. 260, the iodine distilling over into the 
receivers, d. 

It is a solid substance, of a bluish-black color, with a 
metallic lustre, communicates to the skin a fugitive yel- 
low stain, and smells like a sea-beach. It is very vola- 
tile, producing a pale vapor at 60°, and crystallizes in 
rhombic plates and octahedra. The specific gravity is 
4.946. At 220° it melts, and boils at 350°, giving off 
violet fumes. The specific gravity of the vapor is 8.7066. 

Describe the experiment Fig. 259. What are the preparation and 
properties of nitro-mnriatic acid ? From what source is iodine pro- 
cured ? What is the method of its preparation ? What is its ap- 
pearance ? 



PROPERTIES OF IODINE. 
Fig 260. 



287 




o o o o 



Fig. 261. 




It is one of the heaviest gaseous bodies known ; 100 cu- 
bic inches weigh 269.64 grains. 

Iodine supports combustion like chlorine. 
A jar, a, Fig. 261, containing a few grains 
of it, placed in a small sand-bath, 5, and 
warmed by a spirit-lamp, c, may be easily 
filled with its dense vapor, the atmospheric 
air floating out before it. A lighted candle 
plunged in this vapor burns slowly, but phos- 
phorus spontaneously ignites. In the same 
manner, phosphorus, placed with a few grains of solid 
iodine in a capsule covered by a jar, Fut.^% 

Fig. 262, takes fire, with the evolution 
of phosphoric acid, vapor of iodine, and 
iodide of phosphorus. 

Iodine is but sparingly soluble in wa- 
ter, that liquid taking up, if pure, only 
TTnro P ar ^ °f its weight, and becoming 
pale brown. It decomposes in the sun- 
shine, iodic and hydriodic acids arising. 
If the water contain iodide of potassium, chloride of 
ammonium, nitrate of ammonia, or hydriodic acid, it will 
dissolve iodine freely. Alcohol, ether, chloroform, and 

What are its relations as respects combustion ? In what fluids is 
it soluble ? 




288 PKOPERTIES OF IODINE. 

sulphide of carbon also dissolve it abundantly. The 
last fluid is valuable in researches on heat, as it only 
permits the dark rays to pass. 

Iodine gives very characteristic reactions. Iodide of 
potassium with acetate of lead yields a yellow precipi- 
tate, which, on cooling after being boiled, assumes a 
crystalline appearance like flakes of gold leaf. With 
chloride of mercury a scarlet biniodide is produced. If 
dried and sublimed in a tube, the yellow crystals which 
form possess the property of turning red when touched. 
With a solution of starch, free iodine, or an iodide acid- 
ified with nitric acid, yields a blue color; the solution 
becoming colorless if heated, but the color returning on 
cooling, providing the temperature has not been carried 
to the boiling point. If a potato be cut and tincture 
of iodine poured on the surface, innumerable blue specks 
make their appearance, corresponding to the position 
of granules of starch. 

Iodine is most valued for its photographic relations. 
The iodide of silver is one of the most sensitive com- 
pounds at present known. The iodides of potassium, 
ammonium, cadmium, etc., are mixed with collodion or 
albumen, and, a film of the mixture being spread over 
glass, is subjected to the action of a solution of nitrate 
of silver in the dark. After being impressed by the 
light received through a camera lens, a solution of pro- 
tosulphate of iron or pyrogallic acid is poured upon the 
•plate. The parts acted on by light immediately receive 
a dark deposit of metallic silver. The superfluous iodide 
of silver is removed by a solution of cyanide of potas- 
sium or hyposulphite of soda. In the daguerreotype 
the film of iodide is formed by exposing a polished sil- 
ver plate to the vapor of iodine. 

Hydriodic Acid. — HI— 127. 

This gas may be made by dissolving in a solution of 
iodide of potassium as much iodine as it will hold, add- 
ing pieces of phosphorus and distilling. A colorless 
fuming gas is sent over. Its specific gravity is 4.3878 ; 
100 cubic inches weigh 135.89 grains. It extinguishes 

What are its reactions ? How does it act with a solution of starch ? 
What is its most valuable application ? How is hydriodic acid made ? 
What are its properties ? 



HYDRIODIC ACID. 289 

flame and is not inflammable. It liquefies under press- 
ure, and becomes a transparent colorless solid at —60°. 
A solution of hydriodic acid in water may be made by 
passing sulphureted hydrogen from a flask through wa- 
ter in which iodine is suspended. The acid forms, and 
sulphur is deposited : 

i+its=s+iii. 

Hydriodic acid has the general relations of hydro- 
chloric acid, and is, like it, very soluble in water. With 
nitrate of silver it gives a yellow precipitate of iodide 
of silver. 

With oxygen, iodine forms two acids, iodic (I0 5 ) 
and periodic (IO n HO). The former is obtained by 
boiling iodine with the strongest nitric acid. With ni- 
trogen it gives an iodide (JY2tT 2 ), which is prepared by 
putting powdered iodine in aqua ammonia. The brown 
powder which forms is dangerously explosive. If 
placed while moist on paper, it will, on drying, blow 
up flies that may w T alk upon it. Chlorine forms two 
instable compounds — ICl, a liquid; and ICI& a solid. 



LECTURE LIV. 

Beomine. — Sources.— £ Properties. — Compounds. — Flu- 
orine. — Sources. — Hydrofluoric Acid. — Etching on 
Glass. — Carbon. — The Carbon Group. — Allotropic 
Forms of. — Preparation of Char coed and Lamp- 
black. — Diamond. — Absorbent Power of Charcoal. — 
Oxygen Compounds of Carbon. — Carbonic Oxide. — 
Preparation and Properties. — Chloro-carbonic Acid. 

Bromine, Pr=l8, 
occurs in sea-water, and also in certain brine-springs, 
both in America and Europe. It is found, among min- 
erals, associated with silver. From its solutions it may 
be obtained by evaporating the water until the chloride 
of sodium has crystallized out, and passing a current 

How may a solution of it be made ? What arc the oxygen com- 
pounds of iodine? What are the properties of iodide of nitrogen ? 
From what source is bromine obtained ? Describe the method pur- 
sued. 

N 



290 BROMINE. 

of chlorine gas through it. The solution turns yellow, 
and on being agitated with ether the bromine is dis- 
solved out. The ether is agitated with potassa, bromate 
of potassa and bromide of potassium forming. On igni- 
tion, oxygen is expelled, and the whole converted into 
the latter salt, from which the bromine may be distilled 
by the aid of peroxide of manganese and sulphuric 
acid. 

It is a liquid of a deep reddish-brown color, a disa- 
greeable odor, whence its name, solidifying at — 1°.6, 
and boiling at 145°. Its specific gravity is about 3., that 
of the vapor 5.39 ; 100 cubic inches weigh 166.92 grains. 
If breathed it produces the effect of a severe cold, which 
may last for days. It bleaches like chlorine if aqueous 
vapor be present, but not if dry, whence it is supposed 
that the bleaching is produced by nascent oxygen de- 
rived from the decomposed water. It extinguishes 
flame, and combines, with explosion, with potassium 
and phosphorus ; antimony burns in it. In its general 
relations it resembles chlorine. 

With oxygen it forms a compound, bromic acid, 
JBr0 5 \ and with hydrogen, hydrobromic acid, HJBr. 
The latter is prepared by heating a mixture of phospho- 
rus, bromine, and bromide of potassium with water. 
At —100° it is a clear colorless liquid, and becomes solid 
at —124°; 100 cubic inches of the gas weigh 84.53 
grains. 

The bromide of silver is used as a photographic agent, 
in combination with the iodide. 

Fluorine, JF=19, 

is found abundantly in nature, in combination with cal- 
cium, as fluor spar. It occurs also in the topaz, in some 
kinds of mica, in sedimentary rocks, in teeth, and fossil 
bones; these last sometimes contain 10 per cent, of flu- 
oride of calcium. Cryolite, found in Greenland, is a 
fluoride of aluminum and sodium. Fluorine has not 
with certainty been isolated, though it is stated to be a 
yellowish-brown gas. It attacks glass and platinum ; 
and though vessels of fluor spar have been substituted 

What are the properties of bromine ? What other element does 
it resemble ? Describe hydrobromic acid. For what is bromide of 
silver used ? In what forms does fluorine occur ? 



HYDROFLUORIC ACID. 291 

for those, yet the body obtained seems only to have 
been a mixture of chlorine and hydrofluoric acid. 

It possesses an intense affinity for electro-positive 
bodies, and gives rise to a series of compounds resem- 
bling those of chlorine, iodine, and bromine. It does 
not unite with oxygen or carbon. 

Hydrofluoric Acid, JIF=z20, 
is made by decomposing fluoride of calcium by sulphu- 
ric acid in a vessel of platinum or lead, the vapors being 
conducted into a receiver kept at a low temperature. 
The action is 

CaF+HO, 80 3 =CaO,S0 3 +IIF 
It is a clear liquid, fuming in the air, boiling at 68°, and 
having a specific gravity of 1.06. Its attraction for wa- 
ter exceeds that of oil of vitriol, and it produces a ma- 
lignant ulceration of the skin. 

If a piece of glass be coated over with a thin film of 
beeswax, and letters or other marks made through the 
wax to the glass with a pointed tool, on setting it over 
a tin vessel in which, from a mixture of fluor spar and 
sulphuric acid, hydrofluoric acid vapor is escaping, the 
glass is corroded away, or etched in the uncovered 
parts. The liquid acid may also be employed, but the 
letters are then not so visible. 

Carbon. (7=6. 

The carbon group of metalloids comprises three bod- 
ies — carbon, boron, and silicon. They are remarkable 
for being, in the crystalline state, very hard ; in the 
amorphous state, insoluble and non-volatile. Carbon is 
the principal constituent of the organic, and silicon of 
the inorganic kingdom. 

Carbon occurs under many different allotropic condi- 
tions. 1. Diamond, which crystallizes in octahedrons, 
is transparent, incombustible except in oxygen gas, and 
the hardest body known ; hence its use in cutting glass. 
2. Gas carbon, which, unlike diamond, is a good con- 
ductor of electricity, and is opaque. 3. The various 

Are its properties known ? How is hydrofluoric acid made ? 
What remarkable quality does it possess ? What is the carbon 
group, and what are its peculiarities? State the allotropic modifi- 
cations of carbon. 



292 



CARBOX. 



263. 



forms of charcoal, anthracite, and coke. 4. Plumbago, 
which has a metallic lustre, is opaque, and so soft and 
unctuous that it is used to relieve the friction of ma- 
chinery and for writing on paper. 5. Lampblack, a 
powerful absorbent of light and heat, and possessing 
such strong affinity for oxygen that it can take fire 
spontaneously in the air. 

Other forms might be cited; these, however, are 
enough to establish the fact that this simple body fur- 
nishes varieties which differ more strikingly from each 
other than many different metallic bodies. It is no 
doubt owing to the many different states in which car- 
bon exists that its compounds, though containing the 
same proportions of the same ingredients, yet vary so 
much in properties. 

Charcoal is made by the ignition of wood in close 
Fig. vessels, the volatile materials being dissipated and 
the carbon left. The nature of the process may 
be illustrated by taking a slip of wood, &, Fig. 263, 
and placing the burning extremity in a test-tube, 
a. This retards the access of the surrounding air, 
and, as the combustion proceeds, a cylinder of 
charcoal is left. 

Lampblack is formed on 
a similar principle. In the 
iron pot a, Fig. 264, some 
pitch or tar is made to boil, 
a small quantity of air being ad- 
mitted through apertures in the 
brick-work. Imperfect combus- 
tion takes place, the hydrogen 
alone burning, the carbon being 
carried as a dense cloud of smoke 
into the chamber b c by the 
draught. In this there is a hood 
or cone of coarse cloth, d, which 
may be raised or lowered by a pulley.. The sides of 
the chamber are covered with leather, and on these 
the lampblack collects. One of its principal uses is in 
making printer's ink. 

Diamond is the purest form of carbon. Its specific 

What effect do these modifications have on its compounds? How 
is charcoal made ? How is lampblack made? 



Fig. 2G4. 




CAKBON. 293 

gravity is 3.5. It exhibits a high refractive and dis- 
persive action upon light. The largest diamond known 
was the Koh-i-JSToor, which weighed 900 carats when 
found ; in 1852 it was cut into a brilliant of 162| carats. 
The Pitt diamond, one of the crown jewels of France, 
is probably the finest in the world. Its estimated value 
is $2,400,000 ; the Koh-i-Noor is valued at $3,000,000. 
Diamonds have been found in North Carolina. 

Charcoal possesses, in consequence of its porous struc- 
ture, the quality of absorbing many times its own vol- 
ume of different gases. One cubic inch of newly-made 
charcoal will take up of 

Olefiant Gas 35. 

Carbonic Oxide 9.42 

Oxygen 9.25 

Nitrogen 7.50 

Light carbureted Hydrogen 5. 
Hydrogen 1.75 



Ammonia 90 

Hydrochloric Acid 85 

Sulphurous Acid 65 

Sulphureted Hydrogen.. 55 
Protoxide of Nitrogen... 40 
Carbonic Acid 35 



The temperature of the charcoal rises as the gas is con- 
densed. Freshly-burned charcoal, put in a mixture of 
"oxygen and sulphureted hydrogen, will cause a violent 
explosion. It also possesses the power of removing 
foul effluvia.' Ivory black or animal charcoal, which is 
made by the ignition of bones in close vessels, has the 
valuable quality of removing organic coloring matters, 
as is shown by filtering a solution of indigo or brown 
sugar through it. 

In all its forms carbon is infusible, but when burnt in 
air or oxygen they all give rise to carbonic acid. It 
combines with several of the metals to form carburets, 
those of iron being best known. With oxygen it gives 
several compounds : 

CO, Carbonic Oxide. 

C0 2 , Carbonic Acid. 

C 2 3 , SHO, Oxalic 

C 3 4 , Mesoxalic " 

CO,, 3770, Rhodizonic " 

C b Ot,HO, Croconic " 

Ct0 3 ,IIO, Mellitic 

C 5 3 Pyromellitic " 

Of these, the first two are of most interest, and will 
alone be described here. 

What are the properties of diamond? Give the absorbing power 
of charcoal for various gases. What quality has ivory black ? What 
are the oxygen compounds of carbon ? 




.'.-- ..:.: :■: ::;:zz. 

C..:r : QznxB, 00=14, 
is produced when earl >n is burned in limited supply 
of oxygen, :: an sarbonic acid is assed over red-hot 
iron or ovex red-hot carbon. In these cases :"_r actions 

are C - 1 7=2 

In the first, carbonic acid on ith one atom of car- 

bon and yie. a . : ; : :arbonic oxide ; in the second, it 
.- -..:.- loses Hie atom of oxygen to the 

iron and yields one of carbonic ox- 
ide. If : be prepared 
healing :: acid with oil of - 
riol in a r F\ . :. the de- 
compose i : n g i "': g equal vohnn a 
of carbonic acid and carbonic ox- 
ide. The evolution is the "traction of 
ter from the oxalic acid the I'phnric acid. 
C -ZHO-> SO,. HO => >0,.-2H0 -CO 

The acid may be separated by passing the mixture 
throe." a bottle, \ containing potassst-wster, and the 
>xide soUected : watei but the best process is tc 

: ne part of i i 1 s i e : : tass i wi;h ten of oil of 
vitriol in a retort : the carbonic oxide conies over in a 
state of purity. 

r; : ■::;. As obtained by any of these pro- 

: :■- ses it is a odorless gas, which may 
be kept over water, in which it is 
soluble to the extent of 6 per 
Dent It is without odor, and 

sotic poison. A jet of it* T.\\ 266, 
bums in the air "with a bine flame, 

gravity is 9.674; IOC cubic in .'. : - 

jjh 29.96 grains. Ir Las : 
liquefied. The combustion of : produces 

the blue flame seen on fire. I: is evolved by _ 

e tables, a i ticul aquatic plants. Carbonic 

oxide is a compound radio:... gi via g ::;_::: I : a aerie 
bodies. 

When is carbonic oxide produced ? How may it be prepared from 

:::;.-.: ;. :i ". ? F::~ v.-L^: ^;_-r su:5:-i:t :_:.;•- ;: ":.■;- n^i-:- • V.\...; 
are its properties ? 




CARBONIC ACID. 295 

Chloro- carbonic acid or phosgene gas {CO, CI) is 
formed, under the influence of light, from equal volumes 
of chlorine and carbonic oxide. It is an acid body of a 
pungent odor, and is decomposed by water. It is re- 
garded as carbonic acid, in which one atom of oxygen 
is replaced by one of chlorine. 



LECTURE LV. 

Carbonic Acid. — Prepared by Decomposition. — Re- 
sults from Combustion. — Properties. — Density.— Re- 
lations to Combustion and Respiration. — Solubility 
in Water.— Produced in Animals. — Liquid and Sol- 
id Carbonic Acid.— Light Carbureted Hydrogen. 
—Fire-damp.— Marsh Gas. —Artificial Production. 
— Coal Gas. 
Olefiant Gas. —Preparation. — Properties. — Action 
with Chlorine. 

Carbonic Acid. C0 2 —22. 
Carbonic Acid is commonly prepared by the action 
of dilute hydrochloric acid on chalk, or any carbonate 
of lime, the action being 

CaO, C0 2 +ITCl=CaCl.irO + C0 2 ; 
that is, one atom of carbonate of lime and Fiffm 2 67. 
one of hydrochloric acid yield one atom of 
chloride of calcium and one of water, and 
one atom of carbonic acid gas is set free. 
The process may be conducted in a flask, 
as in Fig. 267, the gas being evolved so 
rapidly that it may be collected over wa- 
ter, though that liquid absorbs its own vol- 
ume at the ordinary pressure. 

Carbonic acid is abundantly formed in many pro- 
cesses. It is the result of the complete combustion of 
carbonaceous bodies ; is evolved during the respiration 
of animals and in alcoholic fermentation. It was called 
fixed air by the old chemists, because a constituent of 
limestone. 

What are the properties of chloro-carbonic acid ? How is carbon- 
ic acid made? From what natural processes does it arise? Why 
was it called fixed air ? 




296 



PROPERTIES OF CARBONIC ACID. 






It is a colorless and transparent gas at common tem- 
peratures, with a faint smell and slightly acid taste. It 
is irrespirable, and acts in a diluted state as a narcotic 
poison; even air, containing one tenth of its volume, 
produces a marked effect ; the atmosphere contains one 
part in 2000. Its specific gravity is 1.527; 100 cubic 
inches weigh 47.087 grains; it may therefore be col- 
lected by displacement. For the same reason, it col- 
lects in the bottom of wells and pits, and often suffo- 
cates workmen who descend into such places. It does 
not support combustion ; a lighted taper lowered into 
a jar partly filled with it is at once extinguished. It 
may be poured from one vessel to another; and if ajar 
of it be poured on a candle, the light is at once put out. 
Its density and other qualities may be well illustrated 
when it is formed by the action of fuming nitric acid on 
carbonate of ammonia, a smoky cloud marking its posi- 
tion and movements. The Grotto del Cane owes its 
peculiarity of asphyxiating dogs to the accumulation of 
this gas in its basin-shaped floor. 

Carbonic acid reddens litmus water, but the blue col- 
or is restored by boiling, the acid being Fig. 2G0. 
driven off by the heat. It is soluble in 
water, which, under pressure, takes up 
five or six times its volume, constituting 

the soda-water of commerce. The 

effervescence of Champagne is due 

to its eseape, and natural waters 

usually contain more, or less of it. 

The solubility may be shown by 

agitating it with water in Hope's 

eudiometer, Fig. 268, or by pass- 
ing it through Nooth's soda-water 

machine, Fig. 269. 
A common test for the presence of car- 
bonic acid in wells is to lower a lighted candle, and if 
its flame be extinguished it is inferred that the gas is 
present ; but it does not follow that a man may safely 
descend into such places though a candle may continue 
to burn ; the air may even then contain twenty per cent, 
of the gas. 

What are the properties of carbonic acid? What are its rela- 
tions to combustion? What results from its great specific gravity? 
What is soda-water ? What is a test for this gas ? 



Fig. 263, 




SOLID CARBONIC ACID. 



297 



If through a tube the breath be made to pass into 
lime-water, a deposit of carbonate of lime renders the 
water milky ; or if the breath be conducted through lit- 
mus water, the color changes to red ; the air thus ex- 
pired from the lungs contains three or four per cent, of 
carbonic acid. A man throws out about eight ounces 
of carbon as carbonic acid every day. 

Under a pressure of thirty-six atmospheres, or by be- 
ing cooled to -—106°, carbonic acid condenses into a liq- 
uid four times more expansible by heat than atmospheric 
air. Thilorier's condensation apparatus is shown in 
Fig. 270. It consists of two iron cylinders— A, em- 

Fig. 270. 




ployed as a retort to generate the gas ; B, as a receiver. 
A is charged with a mixture of carbonate of soda and 
water ; a brass tube, C, containing oil of vitriol, is intro- 
duced into it, and the head is screwed on. A is then 
inverted, and. carbonic acid is generated under great 
pressure. A tube, E, is next made to connect A and B, 
the latter vessel being immersed in ice. The liquefied 
gas distills over into B. A tube, 5, descends nearly to 
the bottom of B, and terminates above in a fine nozzle, 



How can its existence in the breath be proved ? 
liquefied ? Describe the apparatus. 

N2 



How may it be 



298 CAEBUEETED HYDE0GEN. 

e. As soon as the stopcock at the top of B is opened 
the liquid carbonic acid is forced out at e by the press- 
ure of its vapor, it evaporates rapidly, and, in so doing, 
produces great cold. A portion of the gas is solidified, 
and if the jet open into a box, D, the solidified acid col- 
lects as a flocculent, snowy-white deposit. Mixed with 
ether, it produces a temperature of —166°. 

Carbonic acid has acid properties in but a feeble de- 
gree. It contains its own volume of oxygen, and hence 
its density, the weight of carbon added not altering the 
volume of the oxygen in which it is burned. The com- 
mon test for its presence is lime-water, which deposits 
carbonate of lime, a white powder. It is entirely ab- 
sorbed by potassa ; and by taking advantage of this fact 
the most perfect vacuum may be formed. 

Caebon and Hydeogest. 

These substances unite, producing many compounds, 
some of which are solid, some liquid, and others gase- 
ous. They are of course all combustible bodies, but the 
description of most of them belongs to organic chemis- 
try. 

Light Caebtteeted Hydeogen, CH 2 =z8, 

occurs abundantly in coal mines, and forms with air ex- 
plosive mixtures ; it is also formed during the putre- 
faction of vegetable matter under water ; on stirring 
the mud of ponds bubbles of this gas escape — hence the 
name marsh gas. It is also ejected from petroleum 
borings, and serves to heat the engine-boilers. The 
village of Fredonia has been lighted for many years by 
a well discharging carbureted hydrogen. It may be 
obtained artificially by heating acetate of potassa with 
hydrate of baryta. It is a colorless gas, burns with a 
yellow flame, producing carbonic acid and water, and 
is, when pure, fatal if respired. Its specific gravity is 
.5528; 100 cubic inches weigh 17.12 grains. It is the 
fire-damp of coal mines ; choke-damp, which comes after 
its explosion, being carbonic acid. The gas is decom- 

How is solid carbonic acid fo-rmed ? What is the test for carbonic 
acid ? What is the common property of the compounds of carbon 
and hydrogen? Where is carbureted hydrogen naturally formed? 
What are its properties? What are fire-damp and choke-damp? 



OLEFIANT GAS. 299 

posed explosively by chlorine in the light, but is not 
acted on in the dark. 

Coal gas contains this gas principally, associated with 
coke, tar, water, carbonic oxide, carbonic acid, olefiant 
gas, sulphureted hydrogen, hydrogen, ammonia, and ni- 
trogen. Gas is purified by washing with water, con- 
densation by cold water, and by hydrate of lime. Its 
specific gravity is about .65, though, if the coal be dis- 
tilled at a higher temperature, it may only be .345, ow- 
ing to the decomposition of olefiant gas. The same 
volume has then much less illuminating power. In 
London 5,000,000,000 cubic feet are used in a year, pro- 
ducing as much light as 10,000,000,000 of tallow can- 
dles. 

Olefiant Gas, G 2 II 2 —\^ 

may be made by heating one part of alcohol with four 
of sulphuric acid in a flask, a, Fig. Fig. 271. 

271. The vapor of ether which 
comes over with it may be removed 
by causing the gas to pass through 
a small bottle, 5, containing sulphu- 
ric acid, before being collected at 
the trough. 

Olefiant gas is transparent and colorless, burns with a 
beautiful flame, forms an explosive mixture with oxy- 
gen, giving rise by its combustion to carbonic acid and 
water. Its specific gravity is .9674; 100 cubic inches 
weigh 29.96 grains. If mixed with an equal volume of 
chlorine an oily liquid condenses, from w T hich olefiant 
gas receives its name. This is the chloride of olefiant 
gas, or Dutch liquid, which will be described under Or- 
ganic Chemistry. With twice its volume of chlorine, if 
it be set on fire, hydrochloric acid is formed, and carbon 
deposited as a dense black smoke. 

What is the composition of coal gas? How is olefiant gas pre- 
pared ? What are its properties ? From what does it derive its 
name? 




300 CYANOGEN. 



LECTURE LVI. 

Cyanogen. — Preparation. — Liquefaction. — An Elec- 
tro - negative Compound Radical. — Bisulphide of 
Carbon. — Refractive and Dispersive Poivers. 

Boron. — Preparation. — Boron Diamonds. — Boracic 
Acid. — Nitride of — Fluoride of. 

Silicon. — Three Allotropic States. — Silicic Acid. — Flu- 
osilicic Acid. — Compounds of Nitrogen and Hydro- 
gen. — Amidogen. — Ammonia. — Ammonium. — The- 
ory of Berzelius. 

Cyanogen, Cy, or Bicarburet of Nitrogen. 
C 2 N=26. 
Carbon unites with nitrogen, forming a bicarburet 
when these substances are in the nascent state, and in 
presence of a base. It may be obtained by exposing 
the cyanide of mercury to heat, or by heating a mixture 
of six parts of ferrocyanide of potassium and nine of 
corrosive sublimate. 

It is a colorless gas, having a peculiar odor. It burns 
with a beautiful purple flame, dissolves to the extent of 
4J volumes in water and 23 volumes in alcohol, con- 
denses into a liquid by a pressure of 3.6 atmospheres 
- at 45°, as may be shown by heating with 

a lamp cyanide of mercury in a bent tube, 
Fig. 272; the tube being closed at berth 
ends, cyanogen accumulates in the cool 
extremity. Though a compound body, it 
has all the properties and characters of a 
powerful electro -negative element. Its 
specific gravity is 1.796; 100 cubic inches weigh 55.64 
grains. Below —30° it is a transparent solid. A far- 
ther description of it and its compounds will be given 
under Organic Chemistry. 

Bisulphide of Carbon, CS 2 —SS^ 
may be made by passing the vapor of sulphur over char- 
coal ignited in a tube, and receiving the product in a 

How is cyanogen made ? What are its properties ? How may it 
be condensed and solidified ? How is bisulphide of carbon made ? 




BISULPHIDE OF CARBON. 



301 



cold bottle. The apparatus is seen in Fig, 273. Into 

Fig. 2T3. 




the top of a large bottle two tubes, b c, one straight and 
the other bent, are inserted. The bottle having been 
filled with charcoal, pieces of sulphur are dropped in 
through the tube b as soon as the bottle is red-hot. 
The sulphur and carbon unite. The product passes 
along the tubes cf^ cooled by a stream of water from 
the cock d, the water being conducted by a string, 7i, 
into a basin, x. The vapor passes into the bottle n, 
which is partly filled with ice, and the incondensible 
gases pass out through m. It is a transparent liquid, 
specific gravity 1.272, of a very disagreeable odor; has 
the quality of dissolving sulphur and phosphorus, boils 
at 100°, and does not freeze at —60°. It is very vola- 
tile, and produces an intense cold during evaporation in 
vacuo, —80° being reached. Its principal point of in- 
terest is the powerful refractive and dispersive power it 
exerts upon light, a .property which renders it especially 
suitable for making prisms to be used in spectroscopes. 
It is also used as a solvent of sulphur and caoutchouc, 
in the making of vulcanized India-rubber. 

Boron, _B=11, 
is found only in combination with oxygen as boracic 
acid, from which it may be set free by heating to 300° 
with twice its weight of potassium or sodium. It may 
be obtained in the crystalline state by heating to a high 
What is its most valuable property ? From what is boron derived ? 



302 BOEACIC ACID. 

degree 8 parts of aluminum with 10 parts of anhydrous 
boracic acid, and treating the product with caustic soda, 
hydrochloric acid, and nitro-hydrofluoric acid. These 
crystals may present the brilliancy of the diamond, and 
are so hard that they will scratch its surface. The spe- 
cific gravity is 2.68. They only take fire under the 
same circumstances as diamond. The amorphous vari- 
ety is olive-colored, and burns at 600° in the air into 
boracic acid. It combines with nitrogen, chlorine, bro- 
mine, and fluorine. 

Boeacic Acid, J50 3 =:35, 
exists in the volcanic springs of Tuscany, and, combined 
with soda, lime, or magnesia, is brought from India, Nor- 
way, Sweden, and South America. It may be artificial- 
ly prepared by dissolving one part of borax in four of 
hot water, and adding half a part of sulphuric acid. On 
cooling, the boracic acid is deposited in small crystalline 
scales, which may be purified by recrystallization. They 
have a soapy feel, and are soluble in 12 parts of boiling 
or 50 parts of cold water. 

Boracic acid melts at a red heat into a transparent 
glass, which, combined with oxide of lead or bismuth, 
has high refractive powers. Its crystals, raised to 212°, 
lose half of their water. It volatilizes readily when 
boiled in water, and is soluble in alcohol, the solution 
mg.TiL burning with a green flame. The 

experiment may be made in a glass 
instrument, a b, Fig. 274, heated 
by a spirit-lamp, e. It is a very 
feeble acid, and even turns yellow 
turmeric brown like an alkali. At 
a red heat it decomposes the sul- 
phates and phosphates. It is em- 
ployed as a flux for porcelain colors. 

NlTEIDE OF BOEON, BN—25, 

is obtained by heating to redness two parts of sal ammo- 
niac and one of borax. It is an amorphous powder, 
without taste or smell. When calcined with carbonate 

What are the peculiarities of its crystals ? How is boracic acid 
prepared? What are its properties? What color does it give to 
flame ? How is nitride of boron made ? 




SILICON. 



303 



Fig. 275. 



of potassa, it decomposes the carbonic acid and forms 
cyanogen. Heated with steam, it produces boracic acid 
and ammonia. 

Terfluoride of Boron. Fluoboric Acid, BF 2 —§&, 
is formed when a mixture of fluor spar, boracic acid, and 
oil of vitriol is heated in a flask. The gas is of a suffo- 
cating odor, reddens litmus, extinguishes flame, is dis- 
solved by water to the extent of 700 volumes, and forms 
dense white fumes with aqueous vapor. It takes water 
from organic substances, charring them, and can decom- 
pose water. 

Silicon, Si— 22, 
may be prepared by igniting the 
silico - fluoride of potassium, Fig. 
275, with potassium, acting upon 
the resulting substance with water, 
which removes the fluoride of po- 
tassium, and leaves the silicon as a 
nut-brown powder. 

It exhibits three allotropic states, 
the amorphous, graphitic, and the 
regular crystalline forms. Alumin- 
um appears to determine the crystalline form of silicon 
and boron. In decomposing the vapor of chloride of 
silicon by aluminum in a vessel of hydrogen, silicon may 
be obtained in hexahedral prisms that can even cut 
glass. 

The amorphous form burns when heated in air, but if 
previously ignited in close vessels it shrinks in volume, 
increases in density so as to sink in sulphuric acid, and, 
passing into another allotropic state, becomes incom- 
bustible in oxygen. Silicon can deoxidize carbonic acid, 
and unites with chlorine, bromine, and fluorine. 

Silicic Acid, a&'0 3 — 46, 
is one of the most abundant bodies in nature, existing 
under the innumerable forms of the quartz minerals, 
sands, and sandstones. It is found in every soil, in all 
waters, is a constituent of many plants, and forms the 

"What are the properties of fluoboric acid ? How may silicon be 
prepared? What allotropic states does it present? What changes 
occur in it by heating ? What is the constitution of silicic acid ? 




304 



SILICIC AXD FLUOSILICIC ACIDS. 



skeleton of tribes of the lower animals. RoGk crystal 
and flint are pure silicic acid. 

It may be obtained for chemical uses as follows : Hea^ 
rock crystal to redness and quench it in water. Fuse 
one part of this with three parts of a mixture of carbon- 
ate of soda and carbonate of potassa, dissolve the result- 
ing silicate in water, and decompose with hydrochloric 
acid. The silicic acid separates as a gelatinous hydrate, 
slightly soluble in water, which, when washed and dried, 
yields a white insoluble powder. 

Silica is a gritty substance, sufficiently hard to scratch 
glass. Its specific gravity is 2.66. It combines with 
the alkalies in excess to form glass. It requires a high 
temperature for fusion, and is insoluble in any acid ex- 
cept hydrofluoric. At ordinary temperatures the sili- 
cates are decomposed by carbonic acid, and it .is to this 
agency that the disintegration of many rocks is due. 
Soluble glass is made by fusing carbonate of soda with 
sand and charcoal. The soluble mass is sometimes used 
as a paint. 

Fluosilicic Acid, SiF d = 1§, 
results when silica is dis- 
solved in hydrofluoric acid, 
or when fluor spar and sand 
are heated with sulphuric 
acid. It is a colorless acrid 
gas, fumes in the air, extin- 
guishes flame, and may be 
liquefied and solidified. The 
specific gravity is 3.6 ; 100 
cubic inches weigh 112 grs. 
Transmitted from the flask 
which" generates it, a, Fig, 
276, through water, it is de- 
composed, hydrated silica 
being deposited. To pre- 
vent the tube which delivers the gas being stopped up 
by the liberated silica, some quicksilver, e, may be put 
in the vessel c?, and the tube dipped into it, so that the 
bubbles of gas may not come into contact with the wa- 

How is it prepared? What are its properties? What is soluble 
glass ? How is fluosilicic acid made ? 



Fluoride of Silicon. 

Fig. 27G. 




AMMONIA. 305 

ter until they have reached the surface of the metal. 
Sulphuric acid may be introduced through I. In the 
water Kydrofluosilicic acid forms. It may be used as a 
test for potassa, soda, and baryta. 

Niteogen and Hydrogen yield three compounds : 

NH 2 , Amiclogen. 
NH 3y Ammonia. 
NH^ Ammonium. 

Amidogen, iV2^=1.6, 
is a hypothetical compound radical, the existence of 
which in several compounds is inferred. On heating 
potassium or sodium in dry ammonia, one equivalent of 
hydrogen is set free, and a solid substance remains — the 
amide of potassium. This, in contact with water, yields 
potassa and ammonia, 

K,NH 2 +IIO=KO±NH 2 . 
Amidogen is an electro-negative compound radical like 
cyanogen. 

Ammonia. J^S r 3 =l t 7. 

This substance, called also volatile alkali, is an abun- 
dant product of the putrefaction of animal matters, and 
may be obtained from the destructive distillation of 
horn ; hence the name, spirit of hartshorn. It also ex- 
ists in the air, and is a common product of many chem- 
ical reactions. Iron rusting in a damp at- 
mosphere contains a trace of it mixed 
with the oxide. 

It may be obtained by heating in a flask, 
«, Fig, 277, equal quantities of slacked 
lime and chloride of ammonium ; and as 
its specific gravity is only .587, it may be 
collected in a flask or jar, 5, with the 
mouth downward, by displacing the heav- 
ier air. The action is 

NII± Cl+ Ca <9, HO=. Ca Cl+ 2lIO+J\ T II 3 . 
It may also be collected at the mercurial trough, as in 
Fig. 278. 

It is a transparent and colorless gas, of excessive pun- 
gency, and a strong alkali. It may be liquefied at —40°, 

What effect has water on it? How many compounds of nitrogen 
and hydrogen are there? What is amidogen? How does ammo- 
nia arise ? How may it be procured ? 




306 



AMMONIA. 

Fig. 278. 




and solidified at —103°, the liquid being most easily ob- 
tained by heating in a sealed tube chloride of silver sat- 
urated with the gas. It turns turmeric paper brown ; 
is absorbed with great rapidity by water, which at 50° 
takes up 670 times its volume, a result which may be 
illustrated by inserting a flask full of it in some cold wa- 
ter, when the water rushes up with sufficient violence to 
destroy the flask frequently. Ammonia neutralizes the 
strongest acids, as may be shown by dropping it into 
litmus water which has been reddened by sulphuric or 
nitric acid. 

It is composed of three volumes of hydrogen with one 
of nitrogen, condensed into two volumes. It may be 
Fig.2"i9. recognized by its remarkable odor, and by 
the formation of white clouds when a rod, a, . 
Fig. 279, dipped in muriatic acid, is ap- 
proached to it. One hundred cubic inches 
weigh 18.19 grains. 

Its solution in water, aqua ammonia, is 
prepared by passing the gas evolved from 
slacked lime and sal ammoniac through Wolfe's bottles, 

What are its properties? How many volumes of it does water 
absorb? What is its effect on reddened litmus? What is its com- 
position ? How is it detected ? How is aqua ammonia made ? 




AQUA AMMONIA. 307 

as is represeentd in Fig. 280. The water will take it 

p Fig. 280. 




up until its specific gravity is lowered to .875. It then 
contains 32J per cent, of gas. At .900 it contains 26 
per cent.; at .951, 12.4 per cent.; at .969, 9.5 per cent. 
This solution is much used for precipitating an^d neutral- 
izing. It affords the best means of obtaining ammonia, 
merely requiring to be warmed in a flask, when the gas 
readily comes off. 

Ammonium, Am-=iNII±=.\% 

is a hypothetical body, believed to be of a metallic na- 
ture; its symbol is Am. It may be combined with 
mercury by decomposing a solution of an ammoniacal 
salt by a Voltaic current, the negative pole being in 
contact with a globule of that metal, or by putting an 
amalgam of potassium and mercury in a solution of sal 
ammoniac. Under those circumstances the mercury 
swells, and eventually becomes of a soft consistency, 
like butter, preserving its metallic aspect completely. 
While the mercury increases to thirty times its volume 
at 100°, it increases in weight only ^oVo-th P art - All at- 
tempts to separate the ammonium from this amalgam, 
which crystallizes in cubes at zero, have failed. It de- 
composes into iVSj and H. 

It is now generally agreed by chemists that ammo- 

What is the nature of ammonium ? In what state may it be ob- 
tained ? 



308 COMPOUNDS OF AMMONIUM. 

nium is the basis of the salts of ammonia, as originally 
stated by Berzelius. Thus sal ammoniac, called also 
the muriate of ammonia, is NH^HCl / this, however, is 
the same as iV2Z^+ Gl ; that is, the chloride of ammo- 
nium. But it must be remembered that when dry 
ammonia and hydrochloric acid gas are brought in con- 
tact a white solid is formed. If this is called chloride 
of ammonium, it would be necessary to suppose that 
the ammonia has taken hydrogen away from chlorine, 
whereas ammonia is itself decomposed by chlorine. 

In all cases where ammonia forms salts w T ith the so- 
called oxygen acids, it requires an atom of water, but 
this water evidently gives it the constitution, not of 
NH^HO, but JVJS^+ ; the water therefore makes 
it oxide of ammonium, which will unite with sulphuric, 
or nitric, or any other acid precisely after the manner 
of any other metallic oxide. Moreover, the compounds 
of ammonia with this atom of water are isomorphous 
with the compounds of potassium. 

Potassium series. Ammonium series. 

Metal K Am 

Oxide KO AmO 

Chloride KCl Am CI 

Sulphide KS AmS 

Nitrate KO, NO b AmO, N0 5 

Sulphate KO, S0 3 AmO, S0 3 

Of the compounds of ammonium with other bodies, 
the protosulphide, JVJI^S, may be mentioned under the 
name of hydrosulphate of ammonia. It is used as a 
test for metals in alkaline solutions. There is also a bi- 
sulphide. 

What is its relation to the ammonia salts? What is the constitu- 
tion of the salts of ammonia with oxygen acids ? Like what class 
of bodies does ammonium act ? What is hydrosulphate of ammo- 
nia ? 



THE METALS, 



LECTURE LVII. 

General Properties oe the Metals. — Definition of 
a Metal. — Color, Specific Gravity, Hardness, Tenac- 
ity, and other Properties. — Relations to Heat. — 
Compounds with other Bodies and one another. — 
Division into Groups. — TJie Oxides and their Re- 
duction. — TJie Sulphides and their Reduction. 

Op the elementary bodies, by far the larger portion 
are metallic. By a metal we mean a body which pos- 
sesses that peculiar manner of reflecting light which is 
known as metallic lustre ; it is also a good conductor of 
heat and electricity. Of these there are about 55 ; the 
number is being continually increased. 

Most of the metals are of a white color, but they dif- 
fer from each other by slight shades, some having a 
faint blue and some a pinkish shade. There are two 
that are strikingly colored — gold, which is yellow ; and 
copper, which is red. In specific gravity they differ 
exceedingly; potassium, sodium, and lithium float in 
water, and iridium is 21 times as heavy as that liquid. 

Many of the metals are malleable — that is, can be ex- 
tended into thin sheets under the blows of a hammer ; 
others are so brittle that they may be reduced to pow- 
der in a mortar; some of them are ductile, and may be 
drawn into fine wires, the order for ductility not being 
the same as that for malleability. Thus iron may be 
drawn into fine wire, but can not be beaten out into 
such thin sheets as many other metals. Of all metals, 
gold is the most malleable, and platinum has been drawn 
into the finest wires, TFoyuTnj^h of an inch in diameter. 

What is the definition of a metal ? How many metals are there ? 
What is their color commonly? Which are the colored metals? 
Which is the lightest, and which the heaviest metal ? Of the met- 
als, which is the most ductile, the most malleable, the softest, the 
hardest, the most fusible? 



310 



PEOPERTIES OF THE METALS. 



la hardness the metals differ much — potassium is so 
soft that it may be moulded by the fingers, but iridium 
is among the hardest bodies known. In tenacity or 
strength the same differences are seen. Of all metals, 
iron is the most tenacious ; a wire one tenth of an inch 
in diameter will sustain a quarter of a ton. The tenaci- 
ty is, as a rule, decreased as the temperature rises. 

In their relations to heat, well-marked distinctions 
may be traced. Mercury, at ordinary temperatures, is 
in a melted condition, but platinum can only be fused 
by the oxyhydrogen blow-pipe or an electrical current. 
As respects volatility, mercury, cadmium, potassium, 
sodium, zinc, arsenic, and tellurium may be distilled or 
sublimed at a red heat. Gold and silver may be vapor- 
ized at a very high heat. 

The metals unite with electro-negative bodies and 
with each other. In decomposition by the Voltaic bat- 
tery they pass to the negative pole, and are therefore 
called electro-positive. Their compounds with oxygen, 
chlorine, etc., pass under the name of oxides, chlorides, 
etc. ; their compounds with each other under the name 
of alloys ; or, if mercury be present, amalgams. They 
also unite with sulphur, phosphorus, and carbon. 

Chemical writers usually divide the metals into groups 
founded upon their relations to oxygen gas. The fol- 
lowing simple division will be adopted in this book : 1st. 
Metals which decompose water at common tempera- 
tures. 2d. Metals which only decompose water at a red 
heat. 3d. Metals which can not decompose water at all. 



1st Group. 


Indium. 


Zinc. 


Potassium. 


Glucinum. 


Cadmium. 


Sodium. 


Zirconium. 


Tin. 


Lithium. 


Thorium. 




Caesium. 


Yttrium. 


3d Group. 


Rubidium. 


Erbium. 


Chromium. 


Barium. 


Terbium. 


Vanadium. 


Strontium. 


Cerium. 


Tungsten. 


Calcium. 


Lanthanum. 


Molybdenum. 




Didymium. 


Osmium. 


2d Group. 


Manganese. 


Columbium. 


Magnesium. 


Iron. 


Niobium. 


Aluminum. 


Nickel. 


Ilmenium. 


Thallium. 


Cobalt. 


Titanium. 


With what other si 


ibstanccs do they unite 


i? Into what groups 



may they be divided ? 



THE METALLIC OXIDES. 311 



Arsenic. 


Lead. 


Palladium. 


Antimony. 


Bismuth. 


Platinum. 


Tellurium. 


Silver. 


Rhodium. 


Uranium. 


Mercury. 


Iridium. 


Copper. 


Gold. 


Ruthenium 



In addition, there are Dianiuin, Norium, and Pelopium, 
the existence of which is uncertain. 

The older chemists divided the metals into four class- 
es: 1st. Alkaline, as potassium; 2d. Earthy, as magne- 
sium ; 3d. Imperfect, as zinc ; 4th. Noble, as gold. 

The Metallic Oxides. 

Metallic substances unite with oxygen with different 
degrees of intensity and in very different proportions, 
many of them giving rise to a complete set of oxides, 
and producing, 1st. Basic Oxides ; 2d. Neutral or Indif- 
ferent Oxides ; 3d. Metallic Acids. 

1st. The basic oxides are commonly protoxides or ses- 
quioxides, which form neutral salts with hydrogen acids 
with the production of water. To form such salts, for 
every atom of oxygen in the base there is required one 
atom of acid. A basic protoxide therefore requires one 
atom of acid, a sesquioxide three, and a deutoxide two, 
to form a neutral salt. 

2d. The neutral or indifferent oxides contain more 
oxygen than the basic, and when heated with acids give 
off the oxygen, a basic oxide resulting. 

3d. The metallic acids always contain most oxygen. 
They may be sesquioxides, deutoxides, teroxides, or 
quadroxides, and are commonly formed by deflagrating 
the metal with nitrate of potassa. 

Reduction of the Metallic Oxides. 

Some of the oxides, as those of mercury, silver, and 
gold, may be reduced by heat alone, but the greater 
number require the conjoint action of carbon, which at 
a high temperature decomposes them, with evolution of 
carbonic oxide. Among powerful reducing agents may 
be mentioned the formiates and the cyanide of potas- 

What was the old division ? What substances do metals yield 
with oxygen? What is the peculiarity of basic oxides; of neutral 
oxides; of metallic acids? By what processes may metallic oxides 
be reduced ? 




312 THE METALLIC SULPHIDES. 

sium, the former acting through the affinity of carbonic 
oxide for oxygen, and the latter through the affinity of 
carbon and potassium conjointly. The deoxidation of 
metals may also be accomplished by reducing agents, 
such as phosphorous and sulphurous acids, or by the ac- 
tion of other metals ; iron, for instance, will precipitate 
metallic copper from its solutions. 

The Voltaic current affords a powerful means of ef- 
fecting the reduction of metals. By its aid the alkaline 
Fig. 281. metals were discovered. The electro- 

type, already described, is an example 
of its action ; solutions of metallic 
salts are readily decomposed by it. 

E W^^^ B Thus ' if a § lass J ar > T > Fi 9- 281 > be di- 
vided into halves, and a paper dia- 
phragm, D, be introduced between 
them, the halves being tightly press- 
ed together by the ring B B, if the 
jar be filled with any metallic solution, such as the sul- 
phate of soda, and the positive and negative wires of 
the battery dipped in the opposite compartments, after 
a time the metallic oxide will be found in one of them 
and the acid in the other, a total decomposition having 
taken place. 

The Metallic Sulphides. 

Many of these, as the sulphides of iron, lead, and cop- 
per, are found abundantly in nature, or they may be 
made artificially by heating the metal with sulphur, or 
by deoxidizing metallic sulphates by charcoal or hydro- 
gen gas, which converts them into sulphides, or by the 
action of sulphureted hydrogen on their oxides, a metal- 
lic sulphide and water being produced. Iron, manga- 
nese, zinc, cobalt, and nickel may be precipitated by hy- 
clrosulphate of ammonia from alkaline solutions. 

The sulphides of a metal are usually equal in number 
and similar in constitution to its oxides ; and as oxygen 
compounds unite with each other to produce oxygen 
salts, the sulphides in like manner also unite with each 
other to produce sulphur salts. 

Describe the experiment Fig. 281. How may metallic sulphides 
be made? What relation exists between sulphides and oxides? 



potassium. 313 

Reduction of the Sulphides. 

The metallic sulphides may often be reduced by melt- 
ing them with another metal having a more powerful 
affinity for sulphur; thus iron filings will decompose 
sulphide of antimony, sulphide of iron forming and an- 
timony being set free. On the large scale, however, a 
different process is resorted to ; the sulphide, by roast- 
ing, is converted into a sulphate, much of the sulphur 
being expelled during the process as sulphurous or sul- 
phuric acid. The resulting sulphate is then acted on by 
lime and carbon at a high temperature ; the lime decom- 
poses the sulphate, setting free the metallic oxide, which 
is at once reduced by the carbon, the sulphate of lime 
turning simultaneously into the sulphide of calcium, and 
floating on the surface of the metal as a slag. 

The metals also unite with chlorine, iodine, bromine, 
carbon, phosphorus, etc., and some with hydrogen and 
nitrogen. These compounds will be described in their 
proper places. 



LECTURE LVIII. 

Potassium. — Discovery and Properties. — Preparation. 
— Relation to Oxygen and 'Water. — Its Oxides. — 
Caustic Potassa. — Tests for Potassa. — Its Existence 
in the Soil and Plants.— Haloid Compounds of Po- 
tassium. — Salts of the Protoxide, the Carbonate, Ni- 
trate, Chlorate, etc. 

Potassium. K— 39. 
Potassium (Kalium) was first obtained by Sir Hum- 
phrey Davy in 1807. He decomposed its hydrated ox- 
ide, potassa, by a Voltaic current. From the positive 
pole oxygen gas escaped in bubbles, and metallic potas- 
sium in globules, together with hydrogen, appeared at 
the negative. 

It was subsequently discovered that the same sub- 
stance could be decomposed by iron, and also by car- 
bon at a high temperature ; and the latter of these sub- 
How may the sulphides be reduced? What is the process on a 
large scale ? How was potassium first obtained ? What process is 
now in use ? 

o 



314 POTASSIUM. 

stances is now exclusively resorted to for the prepara- 
tion of potassium. The carbonate of potassa is ignit- 
ed with charcoal in an iron bottle, and the potassium 
received into a vessel containing naphtha. The pro- 
ductiveness of the operation is greatly interfered with 
by the circumstance that the carbonic oxide which is 
evolved, as it cools below a red heat unites with much 
of the potassium, producing a gray substance, which 
chokes the tubes and diminishes the yield of the metal. 
Not more than one fourth of the potassium contained in 
the carbonate is obtained. 

Potassium is a bluish-white metal, which at 32° is 
brittle, melts at 150°, and boils at a red heat, yielding 
a green vapor. Its specific gravity is .865 ; it is there- 
fore much lighter than water, on the surface of which 
it floats. At 70° it may be moulded with the fingers, 
being soft and pasty. 

It possesses an intense affinity for oxygen, and hence 
Fig. 282. requires to be kept under naphtha, a liquid 
containing no oxygen. A piece of it thrown 
upon water, Fig. 282, takes fire, and burns 
with a beautiful pink flame. In the air it 
speedily tarnishes, as is seen on cutting a 
mass with a penknife ; and even in contact 
with ice there is decomposition with flame. In these 
cases the combustion arises from the hydrogen uniting 
with the oxygen of the air and reproducing water, the 
potassium simultaneously burning into potassa. Potas- 
sium is used for obtaining other metals, as aluminum, 
magnesium, etc., from their oxides. 

Potassium and Oxygen. 

There are three oxides of potassium — a suboxide, a 
protoxide, and a peroxide ; K 2 O, KO, and KO z . 

Suboxide of Potassium , IT 2 0=86 9 

is formed by heating potassium in a limited amount of 
air. It takes fire when heated, and is converted by wa- 
ter into potassa, hydrogen being evolved. 

What interferes with the productiveness of the operation ? What 
are the. properties of potassium ? How does it act on the surface 
of water? Of what use is potassium? How many oxides does it 
form ? How is the suboxide formed ? 




HYDRATED OXIDE OF POTASSIUM. 315 

Protoxide of Potassium, K '0=41, 

is made by heating one atom of potassium with one of 
hydrate of potassa, K+KO, IIO=.2KO+H. 

Hydrated Oxide of Potassium, KO, HO=:56, 

is best procured by boiling two parts of pure carbonate 
of potassa with twenty of water, and, having previously 
slacked one part of quick-lime with hot water, the cream 
which it forms is to be added by degrees, and the whole 
boiled. The process should be conducted in an iron 
vessel, to which a lid can be adapted, so as to exclude 
the air during cooling. The resulting carbonate of 
lime settles, and the hydrate may be obtained by evap- 
orating the solution rapidly in a silver vessel, pouring 
out the melted residue on a silver plate, or casting it in 
the form of small cylinders. 

The decomposition which takes place is very simple : 

KO, C0 2 + CaO, HO= CaO, C0 2 +KO, HO; 

that is, the lime takes carbonic acid from the carbonate 
of potassa, and the oxide of potassium unites w r ith wa- 
ter. The solution may be known to be free from car- 
bonic acid by not effervescing w 7 hen mixed with the 
stronger acids. 

The hydrate of potassa, caustic potash, is a white 
solid, having a powerful affinity for water, and abstract- 
ing it rapidly from the air. Taken between the fingers, 
it communicates to them a soft feeling, and, if a con- 
centrated solution be used, soon effects a disorganiza- 
tion ; it is hence employed by surgeons as an escharotic. 
It possesses pre-eminently the alkaline qualities, and, 
indeed, may be taken as the type of that class of bod- 
ies; neutralizes the most powerful acids perfectly, and 
communicates to turmeric paper or solution a brown 
tint. It turns the reddened infusion of litmus blue, dis- 
solves flint glass, and, possessing an intense affinity for 
carbonic acid, is used in organic analysis to absorb that 
gas. Heated in the blow-pipe flame, it gives a charac- 

How is the protoxide formed? How is the hydrated oxide ob- 
tained? Describe the decomposition. What are the properties and . 
uses of caustic potassa? 



316 POTASS A. 

teristic violet tinge, and in the spectroscope, easily rec- 
ognized lines. 

Potassa in combination occurs in fertile soils, and is 
essential to the growth of land plants, from the ashes 
of which its carbonate is abundantly procured. This 
may be shown by filtering water through the ashes of 
wood, when the clear liquid will be found to answer all 
the tests indicating the presence of potassa. It also oc- 
curs abundantly in feldspar, and hence is found in clays. 
The want of fertility in soils is often due to the absence 
or exhaustion of this body. 

The bichloride of platinum gives, with a solution of 
potassa, a yellow precipitate of the chloride of potas- 
sium and platinum. When the amount of potassa is 
small, it is well to add alcohol at first, in w^hich the dou- 
ble chloride is almost insoluble. Ammonia yields a sim- 
ilar precipitate, but this may be avoided by exposing 
the substance to a red heat before testing. Perchloric 
acid with alcohol yields a white precipitate. Tartaric 
acid, if added in excess, and the mixture stirred w 7 ith a 
glass rod, bearing gently on the sides of the vessel, gives 
white streaks of the bitartrate of potassa wherever the 
rod has passed over the glass. 

Of other compounds of potassium the following may 
be mentioned : 

Peroxide of Potassium, K0 2 
Chloride of Potassium, KCl 
Iodide of Potassium, KI 
Cyanide of Potassium, KCy 
Bromide of Potassium, KBr 
Protosulphide of Potassium, KS 
Tersulphide of Potassium, KS 3 
Ferrocyanide of Potassium, K 2 , Fe, Cf/ 2 

It also combines with hydrogen in two proportions, 
producing a solid and a gas ; the latter takes fire spon- 
taneously in the air. With ammonia it produces po- 
tassiamide, the composition of which is KNH 2 , 

Of these compounds the most important are, 1. The 
peroxfde of potassium, which is formed by burning po- 
tassium in oxygen. It can support combustion, and is 

How may the existence of potassa in plants be shown ? What are 
the tests for potassa? Name some of the other*compounds. What 
is potassiamicle ? What are the properties of the peroxide of potas- 
sium ? 



SALTS OF POTASSA. 317 

decomposed by water, evolving oxygen and leaving po- 
tassa in solution. 2. The chloride of potassium is anal- 
ogous to common salt, and may be formed by burning 
potassium in chlorine. 3. The iodide, much of which is 
consumed in medicine and photography under the name 
of hydriodate of potassa. It is prepared by dissolving 
iodine "in a solution of potassa till the liquid begins to 
appear brown, then evaporating to dryness, and igniting 
the residue ; oxygen is evolved, and iodide of potassium 
remains ; it may then be crystallized from the solution 
in water, the form assumed being that of cubes. It is 
very soluble in water and hot alcohol, and will dissolve 
large quantities of iodine. 4. Cyanide of potassium, 
which is of great use in photography for dissolving 
iodide and bromide of silver, will be described in or- 
ganic chemistry. 5. Bromide of potassium may be 
made like the iodide, and is used as an ingredient of 
collodion in photography on glass. 

Salts of the Peotoxide of Potassium. 

Carbonate of Potassa is obtained by lixiviating the 
ashes of plants. In an impure state it forms the pot- 
ashes and pearlashes of commerce. It may be obtained 
pure by igniting the bitartrate with half its weight of 
the nitrate of potassa. It has an alkaline taste, its solu- 
tion feels greasy to the fingers, it is very soluble in wa- 
ter, which takes up nearly its own weight, and it is 
deliquescent. 

Bicarbonate of Potassa is formed by transmitting a 
stream of carbonic acid through a solution of the former 
salt. It crystallizes in eight-sided prisms with dihedral 
summits, and has most of the properties of the carbon- 
ate. 

Sulphate of Potassa is formed by neutralizing the 
following salt : crystallizes in anhydrous, short, six-sided 
prisms, terminated by six-sided pyramids, soluble in 
twelve times their weight of water, and insoluble in al- 
cohol. 

Bisulphate of Potassa is a residue of the production . 
of nitric acid. It is soluble in water, but is decomposed 

What are the properties of the chloride, iodide, cyanide, bromide 
of potassium ? From what is the carbonate obtained? How are 
the bicarbonate, sulphate, and bisulphate formed ? 



318 SALTS OF POTASSA. 

by an excess of water into the neutral sulphate and acid. 
It crystallizes in rhombohedrons. 

Nitrate of Potassa (Saltpetre) is extracted on the 
large scale from certain soils in which organic matter 
is decaying in contact with potassa. In the Mammoth 
Cave nitrate of lime exists in the soil, and is used to pro- 
duce nitre by decomposition with wood ashes. It crys- 
tallizes in six-sided prisms with dihedral summits ; fuses 
at a heat below redness, with evolution of oxygen gas. 
Its solubility varies greatly with the temperature, 100 
parts of water at 11° dissolving 38 parts, and at 212° 
246 parts. This salt enters as an essential ingredient 
into gunpowder, which is composed of about one atom 
of nitrate of potassa, one of sulphur, and three of carbon. 
The sulphur of this mixture accelerates the combustion, 
while the oxygen of the nitric acid forms carbonic acid 
with the charcoal. The products, therefore, of the per- 
fect combustion of gunpowder are carbonic acid, nitro- 
gen, and sulphide of potassium. It commonly happens, 
however, that sulphate of potassa is form-ed. The pro- 
portions of the ingredients of gunpowder are varied for 
different uses. The powder used for mining, for exam- 
ple, contains more sulphur than that used for fire-arms. 
Gunpowder must be granulated in order to secure its 
rapid combustion. 

Chlorate of Potassa. When a stream of chlorine is 
passed into a solution of potassa, the chloride of potas- 
sium and the chlorate of potassa result ; the latter is de- 
posited in rhomboidal tables. The chlorate of potassa 
is anhydrous; it dissolves in 18 parts of cold water and 
2^- of hot, melts at a red heat with evolution of pure 
oxygen, deflagrates with combustible bodies, as sulphur, 
with much violence. 

What is the origin and use of the nitrate? What is the compo- 
sition of gunpowder ? How is the chlorate made? 



SODIUM. 319 



LECTURE LIX. 

Sodium. — Preparation. — Relations to Oxygen and wa- 
ter. — Color communicated to Flame. — Its Oxides. — 
Tlie Hydrated Oxide. — Tests for Sodium. — Haloid 
Compounds. — Common Salt. — Salts of the Protox- 
ide, Carbonates, Sulphate, Nitrate, Phosphate, etc. — 
Lithium. — Caesium. — Rubidium. — Barium. — Its Ox- 
ides. — Haloid Compounds. — Salts of the Protoxide. 

Sodium. JVd=z2S. 

Sodium (Natrium) may be obtained by the same pro- 
cess as potassium, but is best procured by igniting the 
calcined acetate of soda with powdered charcoal in an 
iron bottle ; and, as the sodium does not act on carbon- 
ic oxide, the operation is much more productive than 
in* the case of the other metal. Like potassium, it has 
to be kept under the surface of naphtha. * 

In color sodium resembles silver ; its specific gravity 
is .97 ; it therefore floats on water. It melts at about 
200°, and is volatile like potassium, its vapor being col- 
orless. Thrown upon water, it decomposes it with a 
hissing sound, and with the evolution of hydrogen, but 
no flame appears. If, however, the water be hot, or 
the metal be put in a muslin bag, then a beautiful yel- 
low flame, characteristic of sodium and its compounds, 
is the result. If a drop or two of water be put on 
freshly-cut sodium, it takes fire. 

Sodium and Oxygen. 
With oxygen, sodium forms three compounds — the 
suboxide, protoxide, and peroxide. 

Protoxide of Sodium. JVa 0=31. 
This, like the corresponding potassium compound, is 
produced by oxidizing sodium in dry air. It is a white 
powder, which attracts moisture from the air, and forms 
the hydrated oxide of sodium, commonly called caustic 
socla. 

How is sodium obtained, and what are its uses? What are its 
properties ? What oxygen compounds does it yield ? 



320 COMPOUNDS OF SODIUM. 

Hydrated Oxide of Sodium, JVa 0+210=40, 
or caustic soda, may be made by the same process as 
that given for caustic potassa, by using carbonate of so- 
da,*and, when the resulting carbonate of lime has set- 
tled, evaporating the liquid. The best proportions are, 
one part of quick-lime to five of carbonate of soda in 
crystals. 

Caustic soda resembles caustic potassa in most of its 
properties. It is deliquescent, has a strong affinity for 
carbonic acid, and acts upon animal tissues as an escha- 
rotic. Its salts are generally jnore soluble than the po- 
tassa salts, and on this are founded the methods recom- 
mended for distinguishing the latter compounds from 
it. Moreover, the soda compounds communicate to the 
flame of alcohol, or to the blow-pipe flame, a yellow 
color, and give in the spectroscope the yellow line D. 

Chloride of Sodium. J¥aCl=58.5. 

Comnfon salt is obtained abundantly from the sea, in 
which it exists to the extent of about four ounces to the 
gallon. It is also found as rock salt, and in brine 
springs. The springs in Onondaga County, New York, 
contain one seventh, and the Great Salt Lake one fifth 
of nearly pure salt in their waters. 

Common salt is the type of that extensive class of 
compounds which have derived the name of salt bodies 
from it. It crystallizes in cubes, and when in mass is 
often perfectly transparent, and permits the passage of 
heat of every temperature through it freely. It melts 
into a liquid at a red heat, and is not more soluble in 
hot than cold water. It is extensively used in the prep- 
aration of hydrochloric acid and chlorine ; immense 
quantities, also, are annually consumed in the prepara- 
tion of carbonate of soda, w T hich is made by first acting 
on common salt with oil of vitriol, so as to turn it into 
sulphate of soda, and, igniting this with charcoal and 
carbonate of lime, an impure carbonate of soda is the 
result, known under the name of black ash, or British 

How is caustic soda made? What are its properties and uses? 
What reactions does sodium yield? What is the constitution of 
common salt? Whence is it obtained? What are its properties? 
To what uses is it put ? 



COMPOUNDS OF SODA. 321 

barilla. Common salt is extensively used for the curing 
of meat. It is also an essential article of food, being 
decomposed in the animal system, and furnishing hydro- 
chloric acid to the gastric juice, and soda to the bile 
and pancreatic juice. 

The compounds of sodium with bromine, iodine, sul- 
phur, etc., are not of interest. 

Salts of the Peotoxide of Sodium. 

Carbonate of Soda is sometimes obtained by lixivi- 
ating the ashes of sea-weeds. Large quantities are now 
procured from the decomposition of sulphate of soda by 
sawdust and lime at a high temperature, the carbonace- 
ous matter decomposing the sulphuric acid and generat- 
ing carbonic acid, which unites with the soda, while the 
liberated sulphur is partly dissipated and partly unites 
with the calcium. From the resulting mass, black ash, 
carbonate of soda is obtained by lixiviation. The crys- 
tals, as found in commerce, contain generally ten atoms 
of water ; there are two other varieties, the one contain- 
ing eight atoms and the other one atom of w r ater» 
Large quantities of the carbonate of soda are also sold 
in an uncrystallized state under the name of salts of 
soda. The figure of the crystals of this salt is a rhom- 
bic octahedron. They effloresce on exposure to the air. 
They are soluble m twice their weight of water at 60°, 
and in less than their own weight at 212°. 

Bicarbonate of Soda, or the double carbonate of soda 
and water, is formed by transmitting a stream of car- 
bonic acid through a solution of the carbonate, and is 
in the form of a white powder. It is less soluble in wa- 
ter than the former, requiring ten parts of water at 60°. 
There is a sesquicarbonate which passes in commerce 
under the name of Trona. 

Chlorinated Carbonate of Soda, or Labarraque's dis- 
infecting liquid, is produced by passing chlorine slowly 
through a solution of carbonate of soda. It is exten- 
sively used for the destruction of noxious odors and ex- 
halations. 

Sulphate of Soda, or Glauber's Salt, occurs as a nat- 

Why is it a necessary ingredient of food ? From what source is 
carr\nate of soda obtained? Describe its preparation. How is 
bicarbonate of soda made ? What is Labarraque's solution ? What 
is Glauber's salt? 

O 2 



322 COMPOUNDS OF SODA. 

ural product, and also as the result of the preparation 
of hydrochloric acid. It is in prismatic crystals of a 
bitter taste, efflorescing in the air, and becoming anhy- 
drous. Water dissolves more than three times its 
weight of this salt at 93°, but above that degree it is 
less soluble. When a solution of three parts of this 
salt in two parts of water is corked up in a flask while 
boiling, it may be cooled without crystallization taking 
place ; but if the cork be withdrawn crystallization at 
once commences, or if it does not, the introduction of 
any solid matter produces it, and the temperature of 
the solution at once rises. 

Nitrate of Soda is found abundantly in different parts 
of America, more particularly in Peru and Chili. In the 
soil it crystallizes in rhomboids. It dissolves in twice 
its weight of cold water, and, from its deliquescence, 
can not be used in the manufacture of gunpowder. 

Phosphate of Soda (tribasic) is formed by neutral- 
izing phosphoric acid with carbonate of soda : two of 
the hydrogen atoms are replaced. It crystallizes in 
oblique rhombic prisms, dissolves in three times its 
weight of cold water, is of an alkaline taste, and gives 
a lemon-yellow precipitate with nitrate of silver. By 
the addition of , soda to it a subphosphate is formed, in 
which all three of the hydrogen atoms of the acid are 
replaced. By the addition of phosphoric acid to the or- 
dinary phosphate till it ceases to give any precipitate 
with the chloride of barium, the biphosphate of soda re- 
sults — a salt very soluble in water. Its crystals are 
rhombic prisms. In it only one of the hydrogen atoms 
is replaced. 

Microcosmic Salt, or the phosphate of soda, ammo- 
nia, and water, is made by dissolving 5 parts of crystal- 
lized rhombic phosphate of soda with 2 of crystallized 
phosphate of ammonia. At a low heat it parts with its 
water of crystallization, and, the temperature rising, it 
loses its ammonia and saline water, becoming monobasic 
phosphate of soda. It is much used in blowpipe experi- 
ments. 

What are its peculiarities of crystallization ? Why can not the 
nitrate be used for gunpowder ? What is the difference between the 
phosphate, subphosphate, and biphosphate? What is raicrocosmic 
salt? 



LITHIUM AND CAESIUM. 323 

Pyrophosphate of Soda (bibasic) is procured by heat- 
ing the phosphate. It gives a white precipitate with 
nitrate of silver. 

Metaphosphate of Soda (monobasic) is formed by 
heating microcosmic salt to redness. It is soluble in 
water, melts at a red heat, and gives, with dilute solu- 
tions of the earthy and metallic salts, viscid precipitates. 

JBiborate of Soda, commonly called Borax. It is im- 
ported in a crude state from the East Indies, and manu- 
factured from the natural boracic acid of Italy by the 
addition of carbonate of soda. It crystallizes in octa- 
hedrons or in oblique prisms, the former containing five, 
the latter ten atoms of water, all of which is lost by ex- 
posure to a red heat, the salt then fusing into a glass. 
It is of great use in blowpipe experiments. 

Hypomlphite of Soda is manufactured on a large 
scale for photographic purposes, because it can easily 
dissolve every compound of silver except the sulphide, 
and that portion of chloride which has been decomposed 
by light. It may be formed by digesting sulphur in hot 
sulphite of soda, or by passing sulphurous acid through 
a solution of sulphite of sodium. 

Lithium, Xi=-7, 
was discovered in 1817, and may be obtained by de- 
composing the chloride by an electric current. It is 
reddish white, softer than lead, and can be pressed into 
wire. It is the lightest known solid element, the spe- 
cific gravity being .594, so that it floats on naphtha; it 
fuses at 356°. Heated in air, it burns with an intense 
white light, forming lithia, Li 0. 

Lithia has only been found to any extent in certain 
minerals, as spodumene, lepidolite, etc. It is character- 
ized by the crimson-red color it imparts to flame, and 
by its spectral lines. It yields a series of salts, chloride, 
'nitrate, sulphate, phosphate, carbonate, etc. 

CLesium, Cfer=133, 
was discovered by Bunsen and KirchhorY in making a 

How are pyrophosphate and metaphosphate of soda formed ? 
From what source is borax derived, and what are its uses? Of 
what use is hyposulphite of soda? In what minerals does lithium 
occur, and what are its properties? What is the characteristic of 
lithium ? 



324 RUBIDIUM AND CAESIUM. 

spectrum analysis of the Durckheim mineral water, 
which contains about three grains of the chloride per 
ton. Its name is derived from the two grayish-blue 
lines peculiar to its spectrum. It decomposes water, 
caesia forming and hydrogen being liberated. The hy- 
drate of ca3sia is soluble in alcohol, corrodes platinum 
like lithia, and is volatile at a high temperature. Among 
the known salts are the chloride, carbonate, nitrate, and 
sulphate. 

Rubidium, i25=r85, 

is named from two intensely red lines which its spec- 
trum has near the end of the less refrangible rays. It 
is commonly associated with csesium, and is found to a 
slight extent (:ro oyotto) i Q sea-water. It may be obtain- 
ed by electrolysis from its chloride. It decomposes wa- 
ter, forming an oxide, Hb 0, which is a powerful base, 
producing a series of salts. These salts, as well as those 
of eaesia, resemble those of potassa closely, in giving, 
with tartaric acid and chloride of platinum, precipitates. 

Barium. Ba =69. 
The existence of barium was first proved by Davy 
in 1808. He isolated it by passing a Voltaic current 
through mercury in contact with hydrate of baryta ; an 
amalgam formed, from which the mercury was subse- 
quently distilled, leaving the barium as a metal of gray 
color like cast iron, heavier than sulphuric acid, the spe- 
cific gravity being 1.5, obtaining oxygen rapidly from 
the air or water, and giving rise to the production of 
baryta, JBa 0. Barium may also be made by passing po- 
tassium in vapor over red-hot baryta. 

Protoxide of Barium, Ba 0=1*1, 
may be obtained by igniting the nitrate of baryta, the 
decomposition being 

BaO, N0 5 =BaO+lSrO A + 0; 
^jat is, one atom of nitrate of baryta yields one of pro- 
toxide of barium, one of nitrous acid, and one of oxygen 
gas. It is a white substance, having a strong affinity 

From what does csesium derive its name ? How is rubidium ob- 
tained, and why is it so called? How was barium first obtained? 
What is the process for obtaining the protoxide? What are its 
properties? 



COMPOUNDS OF BARIUM. 325 

for water, with which, it exhibits the phenomenon of 
slacking, as is the case, to a less extent, with lime, heat 
being evolved. It has an acrid taste, is soluble in water, 
and absorbs carbonic acid from the air. The specific 
gravity is 4., being the heaviest of the earths; hence its 
name. The soluble salts are poisonous. 

Hydrate of Baryta, BaO, HO—QQ, 
is formed by slacking the protoxide, and is a white 
powder, very soluble in hot, but less so in cold water, 
yielding therefore crystals — hexagonal prisms, when a 
hot solution cools ; these contain %en equivalents of wa- 
ter. The cold solution is used as a test for carbonic 
and sulphuric acids, with which it forms insoluble white 
precipitates. 

The solution is most easily obtained by calcining the 
native sulphate with pulverized charcoal, which con- 
verts it into the sulphide of barium. # To a boiling solu- 
tion of this body oxide of copper is added till the liquid 
ceases to blacken a solution of acetate of lead. On be- 
ing filtered, the solution of hydrate of barytes is pro- 
cured. 

Peroxide of Barium, Ba 2 = 85, 
is made by igniting chlorate of potassa with baryta, or 
by passing oxygen over baryta in a red-hot tube. It is 
used in the preparation of the peroxide of hydrogen 
and making of oxygen. 

Of the other compounds of barium, the chloride is 
much used as a test for sulphuric acid. It may be 
made by decomposing carbonate of baryta by hydro- 
chloric acid. The sulphide of barium is made by ignit- 
ing the sulphate of baryta, heavy spar, with charcoal, 
which deoxidizes both the sulphuric acid and the bary- 
ta. It dissolves in hot water, and from this solution 
caustic baryta may be obtained by boiling with the ox- 
ide of lead or copper, and separating the sulphides of 
those metals by filtration. By acting upon it with hy* 
drochloric or nitric acid the chloride or nitrate may be 
prepared. 

How is tlio hydrate formed? How the peroxide? Of what use 
is the chloride ? How is the sulphide made ? 



326 STRONTIUM. 

Salts of the Protoxide of Barium. 

Carbonate of Baryta is found native as the mineral 
Witherite, and may be prepared by precipitating a sol- 
uble salt of baryta with an alkaline carbonate. It is 
soluble in 4300 times its" weight of cold water and 
2300 of boiling. Its density is 4.33. 

Sulphate of Baryta, found native abundantly as 
heavy spar, and from it most of the compounds of bari- 
um are prepared. Its density is 4.47. It crystallizes 
in tabular plates, and is wholly insoluble in water. 



LECTURE LX. 

Strontium. — Uses in Pyrotechny. — Salts of Protox- 
ide. — Calcium.— -Protoxide of — Sources in Nature. 
— Tests for. — Haloid Compounds, Chloride, Fluor- 
ide, Sulphide. — .Salts of the Protoxide, Carbonate, 
Sulphate, Phosphate, Chloride. — Magnesium. — Pro- 
toxide and Salts of. — Aluminum. — Method of obtain- 
ing. — Sesquioxide. — Uses in the Arts. — Salts of. — 
Alums. — Glucinum. — Zirconium. — Thorium. — Yt- 
trium. — Cerium. — Lanthanum. — Didymium. — 
Thallium. — Indium. 

Strontium, Sr=4±, 
is a fixed metal of a gray color, with a reddish reflec- 
tion, having a specific gravity of 2.5. It oxidizes on ex- 
posure to the air, and decomposes water without flame. 
The metal is obtained by electrolysis from the chloride, 
the poles of the battery being of iron. Its natural 
compounds are the sulphate and carbonate. 

Strontium yields a protoxide, which is the basis of a 
series of salts differing from baryta salts in not being 
poisonous. The hydrated protoxide is formed by slack- 
ing the protoxide with water. Strontia gives in the 
spectroscope eight characteristic bands of color — six 
red, one orange, and one blue, but no green. 

What are the properties of the carbonate and sulphate of baryta? 
What are the properties of strontia? What are its spectroscopic re- 
actions ? 



CALCIUM. 327 

Salts of the Protoxide of Strontium. 

Carbonate of Strontia, the strontianite of mineralo- 
gists, is a rare mineral of a greenish tint. 

Sulphate of Strontia, the celestine of mineralogists, 
is found in Sicily, and is of a blue tint. It is not as 
heavy as sulphate of baryta, and is soluble in 3600 parts 
of water. 

Nitrate of Strontia forms an ingredient of the red 
fire of theatres, which is composed of forty parts of it, 
-united with thirteen of sulphur, five of chlorate of po- 
tassa, and four of sulphide of antimony. It crystallizes 
in octahedra, soluble in five parts of cold water and 
one half its weight of boiling water. 

Calcium, Ca=20, 
is obtained by electrolysis from the chloride, and is of 
a yellowish color, harder than lead, malleable, fusible at 
a red heat, burning with scintillations when heated in 
air, chlorine, vapor of bromine, iodine, or sulphur. Its 
specific gravity is 1.57; it decomposes water without 
flame, and yields a protoxide, quick-lime or lime. 

Lime occurs as a carbonate in the various limestones, 
marbles, chalks, etc., which form in many countries ex- 
tensive mountain ranges. Its other salts are very 
abundant. 

From the carbonate, quick-lime may be obtained by 
exposure to a bright red heat. If the limestone con- 
tains silica it may be overburned, a silicate of lime 
forming, which prevents the lime from slacking. It 
possesses a strong affinity for water, and unites there- 
with with a great elevation of temperature, as exhibited 
in the process of slacking, the heat being sufficient to 
inflame gunpowder. Exposed to a high temperature, 
as in the lime light, it phosphoresces splendidly. The 
hydrate which forms when lime is slacked is white ; it 
is soluble to a small extent in water, and it is remarka- 
ble that cold water dissolves more than hot — one part 
of lime requiring 1280 of water at 212°, but only 656 at 
32°. Lime-water is colorless, of a partially caustic 

Describe the carbonate, sulphate, and nitrate of strontia. De- 
scribe calcium. How does lime occur? How is quick-lime pro- 
duced ? What is the action of water on it ? What is lime-water ? 



328 COMPOUNDS OF CALCIUM. 

taste ; neutralizes acids perfectly, restoring to reddened 
litmus its blue color. It is used as a test for carbonic 
acid, with which it gives the white carbonate of lime. 
Milk of lime is lime-water in which hydrate of lime is 
mechanically suspended. The hardening of mortars de- 
pends partly on the formation of carbonate of lime from 
the hydrate that they contain, and partly on the pro- 
duction of a silicate of lime. Hydraulic lime, which 
possesses the property of setting under w 7 ater, contains 
silicate of alumina and oxide of iron. 

Lime is best detected by oxalate of ammonia, with 
which it gives the white precipitate of oxalate of lime 
if the solution be not acid. Lime is valuable in agricul- 
ture from causing the decay of organic matter, and de- 
composing such minerals as yield potassa ? 

Compounds of Calcium. 

Chloride of Calcium, Ca CI =55.5, is formed by dis- 
solving carbonate of lime in hydrochloric acid, and 
evaporating the solution to dryness. It is exceedingly 
deliquescent, and in the uncrystallized state is much 
used for collecting water in organic analysis, and for 
drying gases. It is very soluble in water and alcohol. 

Fluoride of Calcium, CaF=39, called also flu or spar, 
and frequently found associated w^ith lead. It crystal- 
lizes in cubes, octahedrons, etc., of various colors, and 
is procured of many beautiful varieties in Derbyshire ; 
they may be turned in a lathe. It exists in fossil and 
recent bones to a small extent, and is the source from 
which the compounds of fluorine are derived. Chloro- 
phane, one of the varieties, phosphoresces with a pale 
green light when heated. 

Sulphide of Calcium, obtained by -igniting the sul- 
phate of lime with charcoal, or passing sulphureted hy- 
drogen over red-hot lime, constitutes Canton's phospho- 
rus, w T hich may also be made by igniting sulphur with 
oyster -shells. It possesses, when fresh, the curious 
property of shining in the dark after exposure to the 
sunlight or electric spark. 

What does the hardening of mortar depend on ? What is the 
test for lime? For what is chloride of calcium used ? Under what 
forms does fluoride of calcium occur ? What quality does sulphide 
of calcium possess ? 



cakbonate of lime. 329 

Salts of the Protoxide of Calcium. 

Carbonate of Lime is abundantly found in nature, 
forming whole ranges of mountains. The most valua- 
ble white marbles are those which come from Paros, 
Pentelicus, and Carrara. It occurs pure in the form of 
Iceland spar in rhomboiclal crystals possessed of double 
refraction. It is dimorphous, and assumes the form of 
six-sided prisms in the mineral called Arragonite. It is 
anhydrous, insoluble in water, but in water charged 
with carbonic acid it is soluble, and is deposited from 
such a liquid on boiling, or by the diffusion of the car- 
bonic acid into the air. The cart>onic acid is expelled 
from this salt by a red heat and the action of the more 
powerful acids. Carbonate of lime may be obtained in 
union with water by boiling hydrate of lime with sugar. 

The formation of stalactites and stalagmites in caves 
depends on the solubility of carbonate of lime in car- 
bonic acid water. As the water trickles from the roof 
the carbonate is partly deposited in the inverted cone 
suspended from the roof, called the stalactite, and part- 
ly in the cone, the stalagmite, on the floor, as seen in 
Fig. 283. 

Fig. 283. 

-ME" 




Sulphate, of Lime, or Gypsum, occurs native both in 

What are the forms of carbonate of lime ? When does it dissolve 
in water? What arc stalagmites and stalactites? 






330 SALTS OF LIME. 

crystals and in extensive crystalline masses. It con= 
tains two atoms of water, and forms selenite. Alabas- 
ter is also a sulphate of lime. Anhydrite contains no 
water. On calcining the hydrous sulphate of lime at a 
low red heat it becomes plaster of Paris, and has the 
property of setting into a hard mass when made into a 
paste with water. It is then used for making plaster 
casts and for hard-finishing w T alls. The sulphate of 
lime is soluble in 500 parts of water, and communicates 
hardness to it, so that it becomes unfit for washing and 
cooking purposes. 

Phosphate of Lime, or Bone-earth, is a tribasic 
phosphate. It is precipitated when the ash of bones is 
dissolved in hydrochloric acid, and the solution neutral- 
ized by ammonia. It exists native as phosphorite and 
apatite. Phosphate of lime is an important constituent 
of plants, and is necessary in the animal economy to re- 
pair the waste of the bones. Many plants, as the tur- 
nip, can be grown of great size by manuring with 
ground bones. 

Chloride of Lime, or Bleaching Powder, is made by 
exposing hydrate of lime to chlorine. It is a white 
powder, exhaling an odor of chlorine, and is extensively 
employed as a bleaching agent, acidified water being 
used to liberate the chlorineAjChlorimetry is the pro- 
cess for determining the arnotmt of chlorine that chlor- 
ide of lime contains. It is usually about 30 per cent. 

Magnesium. 31g = 12. 
Magnesium was first obtained by Davy in 1808, by 
passing the vapor of potassium over white-hot magne- 
sia, but was not accurately examined until 1830, when 
Bussy prepared it by heating anhydrous chloride of 
magnesium w T ith sodium. It may be procured by elec- 
trolyzing the fused chloride of magnesium. It is a sil- 
very-white, ductile, malleable metal, fusible at a red heat, 
volatile at the same temperature as zinc, and burns with 
great brilliancy, evolving an intensely white light when 
heated in air. This light has been used for producing 

Under what forms does sulphate of lime occur, and what are its 
uses? Of what value is phosphate of lime? What is bleaching 
powder? How is magnesium obtained? What are its properties? 
What are its peculiarities of combustion ? 



MAGNESIUM. 331 

photographs of dark interiors. It is unchanged in dry 
air, and is only slowly oxidized in damp air. It does 
t not decompose water, but is rapidly dissolved by dilute 
acids. It burns when heated in chlorine, and in the va- 
por of bromine, iodine, and sulphur. Its specific gravi- 
ty is 1.74. 

Protoxide of Magnesium. Mg 0=20. 

This substance, called also Calcined Magnesia, or sim- 
ply Magnesia, may be made by heating the carbonate 
to low redness ; the carbonic acid is driven off, and the 
magnesia remains as a w T hite powder, insoluble in water, 
but neutralizing acids completely, and forming with them 
a complete series of salts. 

Magnesia occurs very abundantly in nature, often as- 
sociated as a carbonate with carbonate of lime, as in do- 
lomitic limestone. It also occurs in fertile soils, and is 
essential to the growth of certain plants. 

It is well distinguished from all the foregoing alkaline 
earths by the relation of its sulphate. The sulphates of 
baryta, strontia, and lime form a series of salts, the solu- 
bility of which in water is constantly increasing; to 
these the corresponding magnesia salt may be added ; 
it is very soluble. 

Magnesia is precipitatj^L from its sulphate by the 
caustic alkalies, and by tKte carbonates of potassa and 
soda as a carbonate, but not by the carbonate of ammo- 
nia in the cold. It may be detected by adding carbon- 
ate of ammonia and phosphate of soda in succession, 
when the phosphate of magnesia and ammonia is pre- 
cipitated. Heated before the blowpipe, after having 
been moistened with nitrate of cobalt, magnesia be- 
comes of a pinkish color. 

Salts of the Protoxide of Magnesium. 

Carbonate of Magnesia is found native, and may be 
prepared by boiling the sulphate with an alkaline car- 
bonate, diffusing the precipitate in water, and passing 
a stream of carbonic acid through it ; by spontaneous 
evaporation the carbonate of magnesia is deposited in 
crystals. The carbonate of magnesia, the magnesia alba 

What names are given to the protoxide? What is dolomite? 
How may magnesia be detected ? How is its carbonate prepared ? 



332 ALUMINUM. 

of the shops, is prepared by precipitating the sulphate 
of magnesia with the carbonate of potassa. It occurs 
in light white cubical cakes or in powder, and is not a 
true carbonate, for it does not contain a full equivalent 
of carbonic acid. It is said to be a compound of one 
atom of hydrate of magnesia with three atoms of hy- 
drated carbonate of magnesia. It is very slightly solu- 
ble in water. 

Sulphate of Magnesia — Epsom Salts of commerce — 
is produced by the action of dilute sulphuric acid on 
magnesian limestone. Its crystals are small four-sided 
prisms, soluble in an equal weight of cold and three 
fourths their weight of boiling water, the solution hav- 
ing a bitter taste. A low heat expels six out of the 
seven equivalents of the combined water. 

Phosphate of Magnesia and Ammonia, one of the 
varieties of urinary calculus, may be formed artificially 
when a tribasic phosphate, a salt of ammonia, and a salt 
of magnesia are mixed together. 

Aluminum. Al=z 14. 

Aluminum is obtained by passing the vapor of chlor- 
ide of aluminum over sodium heated in a porcelain tube. 
Intense ignition ensues, and the reduced aluminum forms" 
metallic globules (Al 2 Cl 3 +3JSTa=2Al+3]VaCl). The 
mineral Cryolite, a double fluoride of aluminum and so- 
dium, has also been used as a source of the metal, and 
is decomposed when heated with sodium, yielding glob- 
ules of aluminum imbedded in fused fluoride of sodium. 

Aluminum is a white malleable and ductile metal of 
the hardness of silver. Its specific gravity when rolled 
is about 2.67, and when cast 2.56 ; its point of fusion is 
1750°. It is very slightly acted on by air or w^ater at 
common temperatures. When intensely heated in a 
current of air it suffers only slight oxidation ; heated to 
redness in an atmosphere of steam, it is slowly oxidized. 
It is readily acted on by hydrochloric acid, which evolves 
hydrogen and forms chloride of aluminum. Neither sul- 
phuric nor nitric acid affects it at common temperatures, 
but when boiled in the latter it is oxidized as long as 

What is Epsom Salt? What is the composition of phosphatic 
calculus? How is aluminum prepared? What are its properties? 
Under what circumstances does it oxidize? 



ALUMINA. 333 

the heat is maintained. In concentrated solutions of 
potassa and soda it is oxidized and hydrogen is liber- 
ated. The action is increased when the alkaline solu- 
tion is heated. It forms alloys with many of the other 
metals, but does not combine with mercury. It is not 
affected by sulphur or sulphureted hydrogen. The gen- 
eral characters of this metal are such as to fit it for 
many useful purposes, but its high price has hitherto 
limited these applications. 

Sesquioxide of Aluminum. Al 2 3 =z52. 

This oxide, called also alumina and clay, occurs natu- 
rally under certain forms which are highly prized, as 
the ruby and sapphire. In a more impure condition it 
yields the various common clays, which also contain sil- 
ica or metallic oxides, or other extraneous bodies. 

Alumina may be prepared from the sulphate of alu- 
mina and potassa, common alum, by precipitating the sul- 
phuric acid by chloride of barium. The sulphate of ba- 
ryta goes down, and there is left in the solution chlor- 
ide of potassium and chloride of aluminum. When the 
mass is dried, water is decomposed ; hydrochloric acid 
is then expelled, and alumina, mixed with the chloride 
of potassium, remains behind. The latter is to be dis- 
solved away by water, leaving the alumina as a white 
substance, which, w r ith water, forms a plastic mass, capa- 
ble of being moulded, and retaining its shape when 
baked. After ignition it adheres to the tongue, and 
during the act of drying it contracts considerably in 
volume, a property ivhich formerly gave rise to the in- 
vention of Wedge wood's pyrometer. 

The presence of alumina gives to the clays those prop- 
erties which fit them for the purpose of the potter and 
brickmaker. Alumina is also used as a mordant to fix. 
the colors of certain dyes upon cloth. 

Alumina is precipitated from its solutions by fixed al- 
kalies, which yield a white hydrate of alumina, soluble 
in an excess of the precipitant. It is also thrown down 
by alkaline carbonates, and when these precipitations 
are made in a solution tinged with coloring matter, the 

What are the natural forms of the oxide? How may alumina be 
prepared ? Why is it used in Wedgewood's pyrometer? What is a 
mordant? 



334 PORCELAIN AND EARTHEN-WARE. 

alumina carries it down with it. Such colored precip- 
itates pass under the name of lakes ; and it is this prop- 
erty of attaching such colors to itself, enabling it to 
cause their firm adhesion to cloth fibre, which is the 
cause of its application as a mordant. 

Among the purposes to which alumina is applied may- 
be mentioned the manufacture of Porcelain, and the 
different kinds of earthen-ware. The former substance, 
first made by the Chinese, is very compact and translu- 
cent. It consists essentially of clay mixed with a fusi- 
ble body which binds all its parts together, and is cov- 
ered with a glaze, which does not terminate abruptly 
on the surface, but pervades the substance of the mass. 
In this respect it differs from common earthen-ware. 
Feldspar, or the silicate of lime, are bodies suitable for 
communicating this glassy structure. 

In the manufacture of porcelain great care is taken to 
select clay free from iron. It is mixed with powdered 
quartz and feldspar, and the requisite shape given it 
either by the potter's wheel or by pressing it into 
moulds. It is then dried in the air, and more perfectly 
in a furnace, and, when ignited, forms biscuit. This is 
dipped in the glaze, suspended in water, and becomes 
covered over with a uniform coat of it. It now re- 
mains to dry it once more, and fuse the glaze upon it. 

Earthen-ware consists of a white clay mixed with 
silica. It is glazed with a fusible material containing 
oxide of lead, and colored of different tints by metallic 
oxides ; for example, blue by cobalt. 

Connected with the manufacture of pottery may also 
be mentioned the manufacture of Glass, of which there 
are several varieties, some consisting of silica, potassa 
or soda, and lime, others containing a large quantity of 
oxide of lead. If silica be heated with carbonate of 
potassa and lime, or oxide of lead, carbonic acid is ex- 
pelled and glass forms. The mass is kept in a fused 
condition till it is free from air bubbles, and is then 
cooled until it becomes plastic, so that it may be blown 
or moulded. 

Articles of glass, after they are manufactured, require 

How may alumina be recognized ? What are lakes ? W r hat is 
the composition of porcelain and earthen-ware ? How is glass made ? 
Why must it be annealed ? 



SALTS OF ALUMINA. 335 

to be annealed or slowly cooled down. This allows 
their parts to assume a regular structure, and prevents 
excessive brittleness. 

Soluble Glass is formed when silica is heated with 
twice its weight of carbonate of soda or potassa. It 
derives its name from the fact that it is for the most 
part soluble in water. 

Salts of the Sesquioxide of Aluminum. 

Sulphate of Alumina is made by dissolving alumina 
in dilute sulphuric acid. It enters into the composition 
of the alums. 

Sulphate of Alumina and Potassa {Alum). — This 
important salt is prepared from alum slate. It crystal- 
lizes in octahedrons, has an astringent taste, reddens lit- 
mus paper. It dissolves in about eighteen times its 
weight of cold, and less than its own weight of boiling 
water. It contains twenty-four atoms of water, and, 
when exposed to heat, foams up, melting in its own wa- 
ter, which, being evaporated away, leaves a white po- 
rous mass, commonly called burnt alum. 

In the same way that the sulphate of potassa unites 
with the sulphate of alumina, so also do the sulphates 
of ammonia and of soda, forming respectively the am- 
moniacal and soda alums. The alumina in the common 
alum may be replaced also by the sesquioxides of iron, 
manganese, or chromium, giving iron, manganese, and 
chrome alums. 

Glucinum. G—1. 
Glucinum is obtained by decomposing its chloride by 
means of sodium. It is a gray malleable metal ; specific 
gravity 2.1. Its fusing point is a little below that of 
silver; it is not altered by exposure to air, and is diffi- 
cult of oxidation, even in the flame of the blowpipe. 

Zirconium, Zr=34, 
is procured oy acting on the potassio-fluoride of zirco- 
nium by potassium at a red heat. When cold the prod- 
uct is thrown into water, and the zirconium separates 

What is soluble glass? What are the properties of sulphate of 
alumina and potassa? What other alums are there? How is glu- 
cinum made ? How is zirconium prepared ? 



336 THORIUM. YTTRIUM. 

in the form of a black powder, having the appearance 
of plumbago. It is difficultly soluble in the acids, with 
the exception of the hydrofluoric,- which readily dis- 
solves it, evolving hydrogen. Heated in the atmosphere 
it burns into zirconia. 

Thorium. 2% =60. 

By passing a current of dry chlorine over a mixture 
of thorina and charcoal powder, a crystalline chloride 
of thorium is obtained, which is easily decomposed by 
potassium, and the product is thorium. It is of a gray 
color, metallic lustre, and apparently malleable. It is 
not oxidized by water, but, when heated in the air, it 
burns into thorina. It is feebly acted on by sulphuric 
acid, and scarcely touched by nitric acid ; it is not at- 
tacked by the caustic alkalies at a boiling heat. Hydro- 
chloric acid dissolves it, with the evolution of hydrogen. 

Yttrium, Y==32, 

is obtained by decomposing its chloride by potassium. 
It is gray, brittle, and resists the action of air and water. 
Yttria is always accompanied by Erbia and Terbia^ 
the oxides of two metallic bases, Erbium and Terbium. 
Erbia is pale yellow and terbia pale red, but neither has 
been adequately examined. 

Cerium. (7e=z:46. 

By heating chloride of cerium with potassium an al- 
loy is obtained, which evolves hydrogen when put into 
water, and leaves cerium in the form of a gray metallic 
powder. Heated in the air it burns into an oxide, and 
it is soluble jn the weakest acids, with the evolution of 
hydrogen. 

Lanthanum, ia=44, 

is associated- with cerium. All its salts are said to be 
colorless. When the oxalate is heated it leaves a w T hite 
carbonate, which at a higher temperature is converted 
into a light-brown anhydrous oxide. The white hydra- 
ted oxide attracts carbonic acid so rapidly that it can 

What are the properties of thorium ? What other metals accom- 
pany yttrium ? How is cerium prepared ? What are the properties 
of lanthanum? 



DID YMIUM. THALLIUM. INDIUM. 337 

not be completely washed upon a filter without conver- 
sion into carbonate. 

Did ymium, Di=48, 

accompanies lanthanum and cerium in the minerals con- 
taining the latter metal. The atomic weights attached 
to these metals are of doubtful accuracy. 

Thallium, 27=203, 
was discovered by Crookes in 1861 on account of the 
green line it gives in the spectroscope, whence its name. 
It exists largely in iron and copper pyrites, and in many 
minerals, as lepidolite. It resembles cadmium, being 
white and of a high metallic lustre ; the specific gravity 
is about 11.85. It is one of the softest of the metals, a 
piece of lead scratching it readily ; the melting point is 
561°; it welds at the ordinary temperature. It oxid- 
izes quickly in the air ; does not decompose water, but 
evolves hydrogen from steam at a red heat. 

It forms salts with acids, which are, for the most part, 
colorless and poisonous. The oxides are TIO and 
T10 3 . In Marsh's apparatus it gives a stain resembling 
that of arsenic, but is distinguished from it by exposure 
to iodine, which turns it yellow ; the yellow iodide is 
insoluble in sulphide of ammonium. 

Indium, In— 36, 
was discovered by Reich and Richter in arsenical py- 
rites. It is a lead-gray metal, ductile, and very soft, 
giving a streak on paper. It is most easily detected 
by its spectrum, which contains a line of indigo-blue 
light. Its chloride is very volatile. Heated to a bright 
red, the metal itself volatilizes. 

Where is didymium found ? What are the circumstances of the 
discovery of thallium ? What are its properties ? How is indium 
detected ? 

P 



338 MANGANESE. 



LECTURE LXI. 

Manganese. — Its Seven Oxides. — 1 he Peroxide audits. 
Applications. — Mineral Chameleon. — Acids of Man- 
ganese. — Salts of the Protoxide. — Iron. — Its Natu- 
ral Forms. — Reduction on the Great Scale. — Cast 
Iron. — Wrought Iron. — Steel. — Passive Iron. 

Manganese. Mn =28. 
Manganese may be procured by igniting its oxides 
with a mixture of lampblack and oil in a powerful fur- 
nace, the reduction being somewhat difficult. It is a 
white metal, specific gravity 8.013, requiring a white 
heat for its fusion, and oxidizing readily in the air. It 
is remarkable for the number of oxygen compounds 
which it yields ; they are, 
Mn 0. . .Mn 2 3 ...Mn 2 ... Mn 3 ... Mn 2 7 . . . Mn z 4 

...M?i 4 0~, 
designated respectively, 



Permanganic Acid. 
Red oxide of Manganese. 
Varvicite. 



Protoxide of Manganese. 
Sesquioxide of Manganese. 
Peroxide of Manganese. 
Manganic Acid. 

Of these, the protoxide may be made by passing hydro- 
gen gas over red-hot peroxide of manganese. It is of a 
green color, is a basic body, and forms a series of salts, 
of which the sulphate is used in dyeing. It is isomor- 
phous with magnesia and zinc. Sulphide of ammonium 
yields with it a flesh-colored precipitate, ferrocyanide of 
potassium a white, and the chloride of soda a dark 
brown hydrated peroxide. The sesquioxide is made by 
igniting the peroxide, as will be presently explained. 
The red oxide and varvicite occur as minerals, but, of 
the whole series, the peroxide is by far the most valu- 
able. 

Peroxide of Manganese, Mn (9 2 =44, 
is found abundantly as a mineral, and passes in com- 
merce under the name of black oxide of manganese, a 

How may manganese be obtained ? What are its properties ? How 
many oxides does it furnish? How does the peroxide occur? 



COMPOUNDS OF MANGANESE. 339 

name indicating its color. It is insoluble in water, and 
when exposed to a red heat gives off one fourth of its 
oxygen, forming the sesquioxide, as stated above, the 

action being 

2(Mn0 2 )...=...Mn 2 3 +0. 
On this fact is founded one of the processes for obtain- 
ing oxygen gas. Heated with hydrochloric acid, it 
yields chlorine, as has been explained. It was former- 
ly called glass-maker's soap, from the circumstance that 
it removes, when added to melted glass, the stain of 
protoxide of ir.on, by turning it into peroxide, and causes 
the glass to become colorless ; but if too great a propor- 
tion of peroxide of manganese be used, the glass assumes 
an amethystine color. 

Peroxide of manganese, when ignited with caustic 
potassa in a platinum crucible, yields a substance known 
as Mineral Chameleon, which is of a green color. Wa- 
ter dissolves from it the Manganate of Potassa, which 
is of a beautiful grass-green, the solution speedily pass- 
ing through a variety of shades of purple, blue, and red. 
When mineral chameleon is dissolved in hot water, a 
red solution is obtained of the 

Permanganate of Potassa. The solution of this salt 
is now much employed in volumetric analysis. It read- 
ily parts with its oxygen to organic matter and deoxi- 
dizing bodies generally; it loses its color, and the brown 
hydrated peroxide of manganese is deposited. A stand- 
ard solution is employed for determining the amount 
of organic matter in air and water. It is also used as a 
disinfectant. From the permanganate of baryta a crim- 
son solution of Permanganic Acid may be procured by 
the aid of sulphuric acid. 

Among other compounds of manganese, the follow- 
ing may be named \ 

Protochloride of Manganese, Mn CI = 63.5 
Perchloride " " Mn 2 Cl 7 =S04:.5 

Perfluoride " " Mn 2 Fl 7 =ldd 

The protochloride may be made by acting on the per- 
oxide with hydrochloric acid, evaporating to dryness, 
and fusing at a red heat. On digesting with water, the 

Of what use is it? What is mineral chameleon? What are its 
properties ? Of what use is permanganate of potassa ? How may 
the chlorides of manganese be formed ? 



340 IRON. 

protochloride dissolves, and any impurity of iron is left 
in the state of oxide. Then, by crystallizing, the chlor- 
ide can be obtained in pink crystals. The perchloride is 
produced when permanganate of potassa, common salt, 
and sulphuric acid are heated. It is a dark greenish 
and volatile liquid. The periluoride is obtained by dis- 
tilling sulphuric acid, permanganate of potassa, and fluor 
spar ; it is a greenish-yellow gas. 

Salts of the Protoxide of Manganese. 

Proto sulphate of Manganese, formed by dissolving 
protoxide of manganese in sulphuric acid. The figure 
of its crystals depends on the temperature at which they 
were formed. They have a rose-colored tint. It is in- 
soluble in alcohol, very soluble in water, and is used by 
the dyers to produce a fine brown color. 

There is but one sulphide of manganese. It is ob- 
tained as a hydrate when manganese is precipitated by 
sulphide of ammonium (MnS, HO). It is of a flesh-red 
color. 

Iron. M=28. 

Iron sometimes occurs in a native state and as me- 
teoric iron, also as oxide, carbonate, sulphide, etc. It is 
one of the most abundant of the metals. Much of what 
is found in commerce is derived from clay iron-stone, 
which is an impure carbonate containing silica, alumina, 
magnesia, and other foreign substances. The native 
peroxide of iron, red haematite ; the hydrated peroxide, 
brown haematite ; the black oxide, or magnetic iron ore, 
furnish some of the finer varieties of the metal. 

From clay iron-stone metallic iron is procured by the 
action of carbonaceous matter and lime at a high tem- 
perature. The ore, having been roasted, is thrown into 
the furnace with coal and lime. If the iron is in the 
ore as a silicate, the lime decomposes it at those high 
temperatures, forming a slag of silicate of lime, and the 
oxide of iron set free is instantly reduced by the car- 
bonaceous matter ; the metal, sinking down, protected 
by the slag, is let off by opening a hole in the bottom 
of the furnace. ; 

What are the properties of the fluoride ? What is the use of the 
protosulphate ? What are the forms under which iron occurs ? How 
is it procured from clay iron-stone? 



IRON. 341 

The quantity produced in Great Britain may be esti- 
mated at 3,000,000 tons per annum. 

The substance thus produced is not pure iron ; it con- 
tains carbon and other impurities, and passes under the 
name of cast or pig iron. It is purified by melting and 
sudden cooling, which converts it into fine metal ; this 
fine metal is then melted under exposure to air, which 
burns off the carbon as carbonic oxide, and the mass, 
from being perfectly fluid, becomes coherent. It is now 
subjected to violent mechanical action, such as hammer- 
ing or rolling ; this forces out or burns off the impuri- 
ties, increases its tenacity, and it becomes the wrought 
iron of commerce. 

Cast Iron melts readily at a bright red heat, and ex- 
pands in solidifying ; on this depends its valuable appli- 
cation for making castings. Kept under the surface of 
salt water for a length of time, cast iron becomes con- 
verted into a body somewhat like plumbago, due prob- 
ably to the removal of the iron as a chloride ; the car- 
bon which is left behind is sometimes observed, as it 
dries, to become hot — a phenomenon to be accounted 
for by its porous state. These facts have been frequent- 
ly verified in the case of cannon which have lain for 
years at the bottom of the sea. ^ig. 284. 

.There are two forms of cast 
iron, white and gray ; the for- 
mer contains about five per 
cent, of carbon, the latter three 
or four. The structure of cast 
iron is crystalline, as is shown 
ini%. 284. 

Pure Iron may be obtained by decomposing precipi- 
tated peroxide of iron by hydrogen gas, and melting 
the result. The metal has a bluish color, is more ductile 
than malleable, and is the most tenacious of all the ele- 
ments. It becomes very soft at a red heat, and possess- 
es the welding property; on this depends the art of forg- 
ing it. Its specific gravity is 7.8. It is one of the few 
magnetic bodies, and, when soft, its magnetism is so 
transient that it may gain and lose that quality a thou- 

What are cast iron and fine metal? How is wrought iron made ? 
What are the properties of cast iron ? What changes does it under- 
go in sea-water ? How may pure iron be obtained ? 





342 IRON. 

sand times in a minute. The melting point of iron is 
very high, about 3300°. In the mode of preparing it 
^ nOK from cast iron it does not under- 

go the process of fusion, but its 
particles are simply welded to- 
gether. The fibrous structure 
which wrought iron possesses, 
Fig. 285, is the chief cause of its 
great tenacity; a wire -g^th of 
an inch in diameter will bear a 
weight of sixty pounds. 

Steely which is a valuable preparation of iron, is made 
by placing alternate strata of iron bars and charcoal 
powder in a close box and keeping them red-hot. The 
process is known by the name of cementation. The 
iron gains about 1.5 per cent, of carbon. Steel is muck 
more fusible than iron, and becomes excessively hard 
and brittle by being brought to a red heat, and then 
suddenly quenched in cold water. When allowed to 
cool slowly it is quite soft, but various degrees of elas- 
ticity and hardness may be given to the hardened steel 
by the process of tempering, which is effected by again 
heating it up to a fixed point. Various colors form on 
the surface, which are an index of the temper ; at 460°, 
for example, the color is straw, and the hardness is suit- 
able for fine cutlery. 

The quality of steel is tested by washing its clean sur- 
face with dilute nitric acid, which ought to produce a 
uniform gray color. If the steel be imperfect and con- 
tain veins of iron, they are shown by their difference of 
color; and this is the cause of the veined appearance 
of Damascus steel. Case-hardening is an operation 
performed upon wrought iron, by which it is superfi- 
cially converted into steel. It is accomplished by heat- 
ing to redness in contact with charcoal powder, or by 
the aid of ferrocyanide of potassium. 

By placing a piece of platinum in nitric acid of a spe- 
cific gravity of 1.34, and then bringing an iron wire in 
contact with it and withdrawing the platinum, the iron 

What is the difference in structure of cast and wrought iron? 
How is steel made, and what are its properties ? What is the pro- 
cess of tempering ? How is the quality of steel tested ? What is 
case-hardening? How may iron be rendered passive ? 



OXIDES OF IRON. 343 

assumes a passive or allotropic state. It now exhibits 
no tendency to unite with oxygen, can not precipitate 
copper from its solutions, and simulates the properties 
of platinum and gold. 



LECTURE LXII. 

Iron. — Oxides of. — Three Oxides and Ferric Acid. — 
Tests for Iron. — 'Salts of the Protoxide and Perox- 
ide. — The Sidphides. — Nickel. — Its Reduction from 
the Oxalate. — Cobalt. — Smalt. — Zaffre. — Sympa- 
thetic Iik. — Zinc. — Distillation of — Salts of the Pro- 
toxide. 

Iron and Oxygen. 

Iron burns with rapidity in oxygen gas, as may be 
proved by igniting a piece of it in wire coiled 
into a spiral form in ajar of that gas, Fig, 286, 
when it w^ill be found to take fire and burn 
beautifully. In atmospheric air, under favora- 
ble circumstances, the combustibility of this 
metal may be proved. Thus fine iron filings, 
sprinkled in the flame of a spirit-lamp, burn 
with scintillations. Exposed to air and moist- 
ure, it slowly rusts. Iron yields four oxides : 

Protoxide FeO = 36 

Black Oxide Fe 3 4 =116 

Peroxide Fe^O z ~ 80 

Ferric Acid Fe0 3 === 52 

Protoxide of Iron. FeO—§§. 
This oxide exists, united with acids, in an extensive 
series of salts, from which it is thrown down as a hy- 
drate by alkalies, and is then of a white color, which 
darkens as it passes into the state of peroxide. Ferro- 
cyanide of potassium gives a white precipitate, and the 
ferridcyanide a deep blue. Sulphide of ammonium gives 
a black sulphide of iron. Sulphureted hydrogen and 
gallic acid give no precipitate. 

How may iron be rapidly oxidized? How many oxides does it 
yield? What are the reactions of the protoxide ? 




344 OXIDES OF IRON. 

Black Oxide of Iron. tt 3 4 = 1 1 6 . 

This oxide, known also as the magnet or loadstone, 
is found as a mineral. It is a compound of the protox- 
ide and peroxide. The scales of iron found in black- 
smiths' forges mainly consist of it. It may also be pro- 
duced by decomposing the vapor of water by metallic 
iron in a red-hot tube. 

Peroxide of Iron, Ib 2 O 3 =:S0 9 

is found in nature as oligist iron, or as a hydrate. It 
may be produced artificially as a hydrate by precipita- 
tion from a solution of persulphate of iron by a caustic 
or carbonated alkali, or in a pure state by igniting green 
vitriol ; there is then left a red powder, known as rouge, 
used for polishing metals. This oxide is not magnetic; 
it is the basis of a series of salts, which yield, with alka- 
lies, a brown hydrated peroxide ; with ferrocyanide of 
potassium, Prussian blue ; with sulphocyanide of potas- 
sium, a blood-red solution ; with tannin and gallic acid, 
a black. This last is of considerable interest, constitu- 
ting the basis of ordinary ink. 

The presence of iron can always be determined by 
passing it into the condition of peroxide, and applying 
the foregoing tests. 

Ferric Acid, Fe0 3 — 52, 

is prepared by heating peroxide of iron with four parts 
of nitrate of potassa. The result is treated with cold 
water, which yields a red solution of the ferrate of po- 
tassa. This slowly decomposes in the cold, and very 
rapidly when the solution is warm. The ferrate of ba- 
ryta precipitates when the potassa solution is acted on 
by a soluble salt of baryta. It is a permanent body, of 
a crimson color. 

Among other compounds of iron, the following may 
be named : 

What is the magnet.? What are the natural forms of the perox- 
ide? How may it be prepared? For what is it used? What are 
its reactions ? How is ferric acid made, and what are its proper- 
ties? 



COMPOUNDS OF IRON. 345 

Protochlorideoflron Fed = 63.5 

Perchloride " Fe a O, = 162.5 

Protiodide " Fel =154 

Protosulphide " FeS = 44 

Sesquisulphide " Fe 2 S 3 =104 

Bisulphide " FeS % = 60 

Of these, the protochloride is formed by passing hydro- 
chloric acid over red-hot iron : it is <white, but forms a 
green solution in water. The perchloride, in solution, 
by dissolving peroxide of iron in hydrochloric acid. 
The protiodide, by boiling an excess of iron filings with 
iodine, and evaporating ; it forms, on cooling, a dark 
gray mass. Its solution absorbs oxygen from the air. 
The protosulphide of iron, which is much used for form- 
ing sulphureted hydrogen, may be made by heating a 
mass of iron to a white heat, and applying to it roll sul- 
phur, and receiving the melted globules in a bucket of 
water ; it may also be procured by igniting iron filings 
with sulphur. The bisulphide occurs abundantly as a 
mineral of a golden-yellow color, crystallized in cubes 
or allied forms, and known as Iron Pyrites. It fre- 
quently assumes the form of various organic remains, 
being one of the common petrifying agents, but in this 
state differs * essentially from the cubic pyrites both in 
color and oxidizability, these fossil remains rapidly de- 
caying under exposure to the^ air, but the other form be- 
ing unacted on. Besides these, there is a sulphide of 
iron which is magnetic. 

Salts op the Protoxide op Iron. 

Carbonate of Iron may be obtained from the sulphate 
by an alkaline carbonate, falling as a whitish precipitate. 
It turns brown, however, from the absorption of oxy- 
gen. It occurs as a mineral in spathic iron, and dis- 
solves in water containing carbonic acid, forming chaly- 
beate waters. 

JProtosulphate of Iron — Copperas — Green Vitriol — 
is prepared largely by the oxidation of iron pyrites, and 
crystallizes in oblique prisms of a grass-green color. It 
has a styptic taste, dissolves in twice its weight of cold 
and three fourths its weight of boiling water. It con- 
Name some other compounds of iron. How may these compounds 
be formed ? What is iron pyrites ? What forms does it present ? 
How is carbonate of iron formed ? How is the sulphate made ? 

P2 



34(5 NICKEL. 

tains seven atoms of water. At a low red heat it be- 
comes anhydrous. In this state it is used for the man- 
ufacture of the Nordhausen sulphuric acid. It is em- 
ployed as a developer in collodion photography. 

Salts of the Peroxide of Ieon. 

Persulphate of Jjron may be formed by adding to a 
solution of the protosulphate of iron half an equivalent 
of sulphuric acid, and peroxidizing by nitric acid. With 
water it forms a red solution. 

The native oxides of iron are, 1. Magnetic iron ore; 
2. Specular and micaceous iron ore, found of singular 
beauty at Elba; 3. Haematite, or red ironstone, compris- 
ing several hydrated varieties ; 4. Bog ore, found in 
marshy places and of recent origin. 

Nickel. iV?=30. 

Nickel may be obtained by igniting its oxalate in a 
covered crucible, carbonic acid escaping, and the metal 
being reduced. 

mO+C 2 3 ... = ...M+2(C0 2 ); 
one atom of the oxalate of nickel yielding one of the 
metal and two of carbonic acid gas. 

Nickel is a white metal, requiring a high temperature 
for fusion. Jt is magnetic, and has a specific gravity of 
8.5. An alloy of nickel and iron forms a principal me- 
tallic ingredient in most aerolites, and in the masses of 
native iron found in various parts of the world, the 
nickel being from 1.5 to 8.5 per cent. With copper it 
forms a hard white alloy, used for coinage in the United 
States. German silver consists of copper 8 parts, nickel 
3 to 4 parts, zinc 3^ parts. It unites with oxygen, form- 
ing a protoxide and sesquioxide, the former yielding 
salts of a green color ; the latter is an indifferent body. 

Salts of the Pbotoxide of Nickel. 
Sulphate of Nickel crystallizes from its solutions with 
seven atoms of water in slender green prisms, which, 
when exposed to the sun, change into an aggregate of 
octahedrons, becoming opaque. 

What are its uses ? How is the persulphate obtained ? What are 
the native oxides of iron ? How is nickel prepared ? What are its 
properties ? When does it occur with iron ? What change takes 
place in sulphate of nickel in sunlight ? 



cobalt. — zikc. 347 

Cobalt, (70=30, 

is generally associated with iron and nickel, and with 
them occurs in meteoric iron. Like the preceding met- 
al, it may be obtained by igniting its oxalate in a cov- 
ered crucible, carbonic acid being disengaged and me- 
tallic cobalt left. It is a pinkish-white metal, requiring 
a high temperature for fusion. Its specific gravity is 
8.9. It is magnetic. It forms a protoxide and a'sesqui- 
oxide, the former being the basis of a class of salts 
which are chiefly of a pink or blue color. Smalt is a 
silicate of cobalt, and Zaffre an impure oxide ; the for- 
mer is used to communicate to paper a faint blue tinge, 
and the blue color which the oxide gives to glass is 
taken advantage of in coloring the common varieties of 
earthen-ware. Cobalt is easily detected upon this prin- 
ciple. 

The chloride of cobalt may be made by dissolving the 
oxide or the metal in hydrochloric acid. It is a pink 
solution, which turns blue when dried. It forms a beau- 
tiful sympathetic ink, for letters written with it, espe- 
cially on paper which has a pinkish tinge, are entirely 
invisible, but become of a bright blue color when the 
paper is warmed, the letters again fading as they be- 
come cool and moist. 

Zinc. Z?iz=z32. 
Zinc is a very abundant metal, immense quantities of 
it occurring in the state of New Jersey and in various 
other places. From zinc blende, which is a sulphide, 
converted by roasting into an oxide, or from p . 28J 
the carbonate brought into the same state by 
ignition, the metal may be obtained by the 
process of distillation by descent. The oxide, 
mixed with charcoal, is introduced into a cru- 
cible which has an iron tube passing through 
a hole in its bottom, as seen in Fig. 287, and, 
the lid being luted on, the temperature is 
raised to a white heat, and the zinc, distilling 
over, may be condensed in water. 

How is cobalt procured? What is smalt? What is zaffre ? 
What are the uses of cobalt ? What is sympathetic ink ? How is 
zinc obtained ? 




348 zinc. 

Zinc is a bluish-white metal, which melts at about 
770°, and, if exposed to a bright red heat in the air, 
takes fire and burns with a brilliant pale-green flame. 
Its specific gravity is about 7. At common temper- 
atures it is brittle, but it may be rolled into thin sheets 
at about 300°, and then retains its malleability when 
cold. During its combustion there arises from it a 
great quantity of flocculent oxide, which formerly went 
under the name of nihil album, or philosopher's wool. 
Among the compounds of zinc may be mentioned 

Protoxide of Zinc ZnO =40 

Chloride " ZnCl=67.5 

Sulphide " ...ZnS =48 

Of these, the oxide is formed, as has been said, dur- 
ing the combustion of zinc. It is also precipitated as a 
white hydrate from its soluble salts by potassa or soda, 
soluble in excess of the precipitant. The chloride may 
be made by the action of hydrochloric acid on metallic 
zinc. It is used in the arts for soldering under the 
name of butter of zinc. The sulphide occurs as a min- 
eral under the name of zinc blende. 

If pieces of hot iron be dipped into melted zinc, they 
acquire the appearance of tin plate, for which they are 
a valuable substitute, inasmuch as the zinced iron is 
prevented from oxidation and rusting by the electrical 
relations of the metals. This is commonly known as 
galvanized iron. 

Salts of the Protoxide of Zinc. 

Sulphate of Zinc — White Vitriol. — This salt is formed 
in the process for procuring hydrogen gas by the action 
of dilute sulphuric acid on zinc. It crystallizes in color- 
less prisms with seven atoms of water, and is soluble in 
two and a half parts of cold water. It has a styptic 
taste, and reddens vegetable blues. There are three 
difFerent subsulphates of this oxide. 

Silicate of Zinc, the electric calamine of mineralo- 
gists, remarkable for becoming electric w T hen heated. 

What is remarkable in rolling it ? What is nihil album ? How 
are the oxide and chloride formed? What is galvanized iron? 
How is white vitriol made ? What is electric calamine ? 



CADMIUM. 349 



LECTURE LXIIL 

Cadmium. — Sources of. — Its Volatility. — Tin. — Block 
and Grain. — Its Properties. — Protoxide and Stannic 
Acid. — Chlorides of Tin. — Mosaic Gold. — Its Uses. 
— Chromium. — Chrome Iron. — Green Oxide and its 
Uses. — Chromic Acid. — Salts of the Sesquioxide. — 
Salts of Chromic Acid. — Vanadium. — Tungsten. — 
Columbium. — Niobium. — Ilmenium. — ISTorium. — 
pelopium. — dlanium. — molybdenum. — tltanium. 

Cadmium. Cd=56. 

This metal was discovered in 1817 by Stromeyer. It 
is contained in certain ores of zinc, and, being more vol- 
atile than zinc, passes over with the first portions of 
metal, from which it may be separated by dissolving it 
in dilute sulphuric acid, and passing sulphide of hydro- 
gen through the solution; the sulphide of cadmium 
thus precipitated is then dissolved in hydrochloric acid, 
and precipitated by carbonate of ammonia. This pre- 
cipitate, after having been washed and dried, is mixed 
with charcoal, and reduced in an earthen-ware retort ; 
the cadmium passes over at a dull red heat. 

Cadmium, in its physical properties, much resembles 
tin, but it is rather harder and more tenacious; it 
crackles when bent. Its specific gravity is from 8.60 to 
8.69. It fuses below the temperature required by tin. 

Bromide and iodide of cadmium are of use in pho- 
tography. 

Tin. Sn=50. 
Tin has been known from remote ages, and was ob- 
tained at a very early period from Spain and Britain 
by the Phoenicians. It occurs most abundantly in Corn- 
wall, the mines of which afford about 3000 tons annu- 
ally. It is also found in Germany, Bohemia, and Hun- 
gary; in Chili and Mexico, in Malacca, India, and the 
island of Banca. The native peroxide is the principal 

How does cadmium occur ? How is it separated ? What are its 
properties ? Where is tin found, and in what form ? 



l 



350 tin. 

ore of tin. It may be reduced by the action of char- 
coal at a high temperature. 

Tin is a white metal like silver. It oxidizes in the 
air superficially, the action ceasing as soon as a thin 
crust is formed. At a red heat it oxidizes rapidly, form- 
ing putty powder, used for polishing metals. It is very 
malleable, and may be rolled into thin foil. When bent 
backward and forward it emits a crackling sound. It 
is very soft; its specific gravity 7.2. It melts at 442°, 
and burns when raised to a high temperature in the air. 
Some of its compounds are 

Protoxide of Tin SnO = 58 

Sesquioxide " Sn 2 3 — 124 

Peroxide " Sn0 2 = 66 

Protochloride " SnCl = 85.5 

Perchloride " SnCl 2 =12l 

Protosulphide " SnS = 66 

Persulphide " SnS 9 = '82 

The protoxide may be made by precipitation from 
the protochloride by carbonate of potassa. It is to be 
washed with warm water, and its water finally driven 
off by a current of carbonic acid gas at a red heat. It 
is of a black color, is easily set on fire in atmospheric 
air, passing into the condition of peroxide. Its salts re- 
duce the noble metals to the metallic state, when added 
to their solutions, and yield with the chloride of gold 
the Purple of Cassius. The peroxide, called also stan- 
nic acid, from exhibiting weak acid properties, may be 
made by the action of nitric acid on tin. It is a hydrate 
in the form of a white powder, insoluble in acids and 
water; but if obtained by precipitation from perchlo- 
ride of tin, it is soluble both in acids and alkalies. 
Melted with glass, it forms a white enamel. 

The protochloride may be made by dissolving tin in 
warm hydrochloric acid. The solution, when concen- 
trated, deposits crystals of the hydrated protochloride. 
These are decomposed when heated. The anhydrous 
protochloride may be made by passing hydrochloric acid 
gas over metallic tin at a red heat. The perchloride is 

State the properties of tin. What is the crackling of tin ? How 
is the protoxide made, and how do its salts act? How is stannic 
acid made? What effect has it in glass? How is the protochlo- 
ride made ? 



CHROMIUM. 351 

procured by distilling eight parts of tin with twenty- 
four of corrosive sublimate. It is a smoking fluid, and 
was formerly called the Fuming Liquor of Libavius. 
A solution of this substance, much used in dyeing, is 
made by dissolving tin in nitromuriatic acid, or by 
warming a solution of the protochloride with a little 
nitric acid. 

Of the sulphides, the first may be formed by pouring 
melted tin on sulphur, and igniting the powdered result 
with more sulphur in a crucible. It is a bluish-gray 
compound. The persulphide is obtained when two 
parts of peroxide of tin, two of sulphur, and one of sal 
ammoniac are ignited in a retort. It is a body of a 
golden-yellow color, formerly called Aurum Musivmn, 
or Mosaic gold, in small scales of a greasy feel, and is 
used for exciting electrical machines, being much more 
energetic than the common amalgam, though less dura- 
ble in its power. 

Tin furnishes several valuable metallic combinations ; 
Tin Plate is sheet iron superficially alloyed with it. 
The soft solders are alloys of lead and tin. Pewter is 
an alloy with antimony. 

Moir& Metallique is tin plate which has been super- 
ficially acted on by an acid so as to display by reflected 
light the crystalline texture of the tin. 

Chromium. Cr = 26. 
Chromium occurs abundantly near Baltimore as the 
chromate of iron ( Chrome Iron), more rarely as the red 
chromate of lead. The metal may be obtained by the 
action of charcoal on the oxide at a high temperature, 
and is of a yellowish-white color. It takes its name 
from its tendency to produce highly-colored compounds. 
It is very infusible, and has a specific gravity of about 
6. Its compounds to be here described are 

Sesquioxide of Chromium Cr 2 2 = 76 

Chromic Acid Or0 3 = 50 

Sesquichloride of Chromium . 2 C7 3 =158.5 

The sesquioxide may be prepared by heating the 

What is the Liquor of Libavius ? How is Mosaic gold made, and 
what is its use ? What is Moire Metallique ? What natural forms 
does chromium present? What is the origin of its name ? How is 
the sesquioxide prepared ? 



352 SALTS OF CHROMIUM. 

chromate of mercury to redness in a crucible. The 
mercury is driven off, and the chromic acid partially de- 
oxidized, leaving a beautiful grass -green powder, the 
sesquioxide. It may also be obtained by heating the 
bichromate of potassa red-hot, and washing the residue 
in water ; also as a hydrate, by boiling a solution, of bi- 
chromate of potassa with hydrochloric acid, and adding 
alcohol ; the mixture becomes of a green color, and am- 
monia precipitates the hydrated sesquioxide. It is a 
weak base, yielding a class of salts of a blue or green 
color. In the state of hydrate it is soluble in acids, but 
on making it red-hot it suddenly becomes incandescent, 
passes into another allotropic state, and is now insolu- 
ble. This sesquioxide is isomorphous with the sesqui- 
oxides of iron and alumina. In its two allotropic states 
it yields corresponding classes of salts, one of which is 
green and the other reddish-green. It is used for com- 
municating a green color to porcelain. 

Chromic Acid may be made by adding one volume 
of a saturated solution of bichromate of potassa to one 
and a half of oil of vitriol. On cooling, red crystals of 
chromic acid are deposited. It is isomorphous with 
sulphuric acid, produces with bases yellow and red salts, 
is a powerful oxidizing agent, is decomposed by a red 
heat into the sesquioxide, destroys the color of indigo 
and other dyes, and may be detected by producing, with 
the salts of lead, chrome yellow, and by its ready pas- 
sage, under the influence of deoxidizing agents, into the 
sesquioxide. 

The sesquichloride is procured when chlorine is pass- 
ed over a mixture of the sesquioxide and charcoal in a 
red-hot tube. It is a lilac-colored body, which forms a 
green solution in w T ater. There is also an oxy chloride, 
which may be distilled as a deep red liquid from a mix- 
ture of chromate of potassa, common salt, and oil of vit- 
riol. The fluoride, which is a red gas, is obtained by 
distilling in a silver retort a mixture of chromate of 
lead, fluor spar, and oil of vitriol. It is decomposed by 
the moisture of the air, forming chromic and hydrofluor- 
ic acids. 
^ 

What is its use? How is chromic acid made ? What is its effect 
on indigo and dyes ? How are the chloride and fluoride obtained ? 



SALTS OF CHROMIUM. 353 

Salts of the Sesquioxide of Chromium. 

Sulphate of Chromium and Potassa ( Chrome Alum) . 
When the oxide of chromium is dissolved in sulphuric 
acid and mixed with the sulphate of potassa and a little 
free sulphuric acid, crystals of chrome alum are deposit- 
ed in red or blue octahedrons. 

Chrome Lron, a compound of the sesquioxide of chro- 
mium and the protoxide of iron, is found native, crystal- 
lized in octahedrons, and also massive. It furnishes 
most of the compounds of chromium. 

Salts of Chromic Acid. 

Chr ornate of Potassa may be made by igniting 
chrome iron with one fifth its weight of nitrate of po- 
tassa. It crystallizes in small lemon-yellow prisms, and 
is very soluble in hot water. The crystals are anhy- 
drous. 

Bichromate of Potassa may be prepared from the 
former by adding an equivalent of acetic acid. It crys- 
tallizes in prisms of a ruby red. Large quantities are 
consumed by dyers. 

Chr ornate of Lead {Chrome Yellow), obtained by pre- 
cipitation from either of the foregoing salts by a solu- 
ble salt of lead. It is used as a paint. 

Diehromate of Lead \s formed by adding chromate 
of lead to melted nitrate of potassa, and dissolving out 
the chromate of potassa and excess of nitre by water. 
It is of a beautiful red color. 

Vanadium, V— 6 8, 

occurs in certain lead ores, and may be obtained by de- 
composing the chloride by a current of dry ammonia in 
a glass tube heated over a spirit-lamp. It has a silvery 
lustre, is brittle, and not acted upon by air or water at 
common temperatures. At a dull red heat it burns into 
a black oxide. It is not dissolved by sulphuric or hy- 
drochloric acids, but nitric acid and nitro-hydrochloric 
acid yield with it dark blue solutions. It has three 
oxides, VO, V0 2 , V0 3 . * 

What is chrome alum? What is chrome iron? How are the 
chromates of potassa made? What is chrome yellow? How is 
vanadium prepared, and what are its properties ? 



354 TUNGSTEN, ETC. 

Tungsten, W— 92, 
is obtained by passing hydrogen over ignited tungstic 
acid mixed with charcoal. It is very difficult of fusion, 
hard, brittle, and of an iron -gray color. Its specific 
gravity is 17.6. It is oxidized by the action of he^t and 
air, and by nitric acid. It communicates valuable prop- 
erties to steel. Tungsten is also called Wolframium, 
from Wolfram, which is a tungstate of iron and man- 
ganese. 

Columbium, Ta =184, 
called also Tantalum, was discovered in a North Amer- 
ican mineral, Columbite, in 1801. It is obtained by heat- 
ing potassium with the potassio-fmoride of columbium, 
and washing the mass in water. It remains in the form 
of a black powder, which, on pressure, resembles iron. 

Niobium — Ilmenium — Nokium — Pelopium — Dianium. 
Among these rare metals, the two first mentioned 
have been announced as associated with columbium in 
some varieties of tantalite, but their distinctive charac- 
ters have been, as yet, very imperfectly ascertained. 
Niobium is considered by some chemists to be colum- 
bium, while the metal pelopium has no independent ex- 
istence, the pelopic and niobic acids being identical. 
Another metal of this series is called Dianium, but Da- 
ville states that dianic acid is hyponiobic acid. 

Molybdenum, 3£o— 48, 
is a whitish, brittle, and very difficultly fusible metal, 
forming three compounds with oxygen, Mo 0, Mo 2 , 
Mo 3 . A salt of the last, the molybdate of ammonia, 
is useful as a test for phosphoric acid. 

Uranium, U=60 y 
is a white, slightly malleable metal, unchanged by air 
and water at common temperatures. Its peroxide, 
TT 2 0^ is used to give a greenish-yellow color to glass. 
The nitrate of uranium is of use in photography. 

How is tungsten prepared, and what are its properties? How is 
columbium prepared ? What remarks are to be made about the rare 
metals niobium, etc. ? Of what value is molybdenum ? What are 
the properties of uranium ? 



ARSENIC. 355 

Titanium, Ti= 24, 

exists as titanic acid, Ti0 2 , in Rutilite, Anatase, and 
Oysanite. Titanic acid is useful in the coloring of the 
gums of artificial teeth and in porcelain painting. 



LECTURE LXIV. 

Arsenic. — Preparation of the Metal. — Properties of 
Arsenious Acid. — Two Varieties of it. — The meth- 
ods of detecting it. — Process in Cases of Poisoning. 
— Sulphitreted Hydrogen Test. — MafeHs Test. — The 
Copper Test. — Difficulties arising from Antimony. 

Arsenic. As =15. 

Arsenic is obtained by sublimation in a current of 
air of the arsenide of cobalt and iron, the vapor condens- 
ing as a white oxide. This being mixed with powder- 
ed charcoal or black flux, and heated, the metallic arse- 
nic sublimes. The process may be conducted in Fig.zss. 
a tall vial, JFig. 288, imbedded in a crucible filled 
with sand, two thirds of the vial projecting above j 
the heated sand. On this cooler portion the met- 
al condenses. It is also sometimes found in a na- 
tive state. 

Arsenic is a metallic body, of a steel-gray color. It is 
very brittle ; its specific gravity is 5.88, and, when slow- 
ly sublimed, it crystallizes in rhombohedrons. At 400° 
it sublimes without undergoing fusion, its melting point 
being much higher than that of sublimation. Its vapor 
has a smell of garlic, as may be readily recognized by 
throwing a little arsenious acid on a red-hot coal. Ar- 
senic prepared by black flux tarnishes, it is said, from 
containing a little potassium. Among its compounds 
the following may be mentioned : 

Arsenious Acid As0 3 = 99 

Arsenic Acid As 5 = 1 1 5 

Bisulphide of Arsenic AsS 2 = 107 

Tersulphide of Arsenic AsS 3 —123 

Arseniureted Hydrogen AsII 3 = 78 

How does titanium exist ? How is metallic arsenic obtained ? 
What are its properties? What is its odor? 



356 ARSENIOUS ACID. 

Arsenioiis Acid is formed when arsenic is sublimed in 
atmospheric air. It is a white substance, which, when 
the process is conducted slowly, crystallizes in octahe- 
drons. Similar octahedral crystals may be obtained by 
heating arsenious acid itself in a tube to 380°. When 
the operation has been recently performed and a large 
mass sublimed, it is a glassy, transparent body, which in 
the course of time slowly becomes milk-white. The spe- 
cific gravity of arsenious acid is 3.7. It is nearly taste- 
less, of sparing solubility in water, the two varieties dif- 
fering in this respect. By 100 parts of boiliug water, 
11.5 of the opaque, but only 9.7 of the transparent, are 
dissolved. ThU substance passes currently under the 
name of arsenic. It ought not to be forgotten that the 
arsenic of chemical writers and that of commerce are 
very different bodies : the one is black and the other 
white ; the one is a metal and the other its oxide. 

Arsenious acid may be detected by several methods : 

1st. With ammonia sulphate of copper it gives an 
emerald - green precipitate — the arsenite of copper, or 
Scheele's green. 

2d. With the ammonia nitrate of silver, a canary-yel- 
low precipitate — the arsenite of silver. 

3d. With sulphureted hydrogen, when previously 
acidulated with acetic or hydrochloric acid, it yields a 
yellow precipitate, the tersulphide of arsenic, orpiment. 
This, when dried and ignited with black flux (a mixture 
of charcoal and carbonate of potassa, obtained by ignit- 
ing cream of tartar in a covered crucible), yields a sub- 
limate of metallic arsenic. 

4th. With the materials for generating hydrogen gas — 
that is, sulphuric acid, zinc, and w T ater, placed in a bot- 
tle — if arsenious acid be present, arseniureted hydrogen 
is disengaged. When set on fire, it burns with a pale 
blue flame, emitting a white smoke ; and if a piece of 
cold glass be held in the flame, there is deposited upon 
it a black spot of arsenic, surrounded by a white border 

How is arsenious acid made ? What is its crystalline form ? What 
is the difference between the arsenic of chemists and that of com- 
merce ? What is the action of arsenious acid on ammonia sulphate 
of copper? With ammonia nitrate of silver ? With sulphureted hy- 
drogen ? What is the process for detecting it as arseniureted hy- 
drogen ? 



TESTS FOE. AKSENIC. 



357 



of arsenious acid. This stain is volatilized on heating 
the glass. Or if the arseniureted hydrogen be conduct- 
ed through a tube of Bohemian glass, made red-hot at 
one point by a spirit-lamp, it is decomposed, and metal- 
lic arsenic deposited on the cooler portions beyond the 
ignited space. 

5th. If a solution containing arsenious acid be acidu- 
lated with hydrochloric acid and boiled with slips of 
copper, the metallic arsenic is deposited upon the cop- 
per as an iron-gray crust. This is called Reinsch's test. 

In cases of poisoning by this substance, it is unsatis- 
factory to apply, in the first instance, color-giving tests, 
such as the first, second, and third, as the liquor obtain- 
ed from the stomach is itself highly colored and turbid. 
It is therefore desirable to examine that organ and its 
contents minutely, endeavoring to discover any white 
granules, or specks, which may be supposed to be arse- 
nious acid, and, if such are found, to examine them sep- 
arately. 

The contents of the stomach, the larger pieces having 
been divided, are to be boiled in water and strained 
through a linen cloth. A current of chlorine gas pass- 
ed through this liquid coagulates and separates much of 
the animal matter ; or, what is more convenient, if the 
solution be first acidulated with nitric acid, and then ni- 
trate of silver be added, much of the animal matter may 
be removed. By the addition of a solution of common 
salt, the excess of the silver salt may be precipitated, 
and the liquor, being filtered, is then fit for the third or 
fourth of the foregoing tests. 

In the application of sulphureted hydrogen, the liquor 
having been clarified as just stated, tne gas is passed 
through it until it smells strongly. It is then to be 
boiled for a short time, to expel the excess of gas, and 
filtered. The yellow precipitate of tersulphide of arse- 
nic, or orpiment, which is collected, is to Fig. 2S9. 
be thoroughly dried, and introduced, with 
twice its bulk of black flux, into the bulb, 
a, of a tube, such as Fig. 289, made of ^ 
hard glass. On the temperature being 

What is Keinsch's test ? When are color tests applicable ? What 
is the method of testing a stomach ? Describe the sulphureted hy- 
drogen test. 




358 



MARSH S TEST. 




raised by a lamp, metallic arsenic sublimes, forming an 
iron-black ring round the part b. By cutting off the 
bulb of the tube and heating the black crust gradually, 
it slowly sublimes toward the colder part, producing a 
white deposit of arsenious acid in octahedral crystals. 
In the application of MarsKs test, the liquor, having 
Fig. 290. been cleared either by chlorine or by ni- 
trate of silver, as above described, and 
mixed with a little sulphuric acid, is to be 
introduced into an apparatus, A B, Fig. 
290, composed of a bent glass tube, one 
arm of which, B, is longer than the other. 
A piece of zinc is suspended by a thread 
in the arm A, so that it shall not reach the 
curved part. The liquid, on being poured 
into B while the stopcock above A is open, 
at first fills A, but, as hydrogen commences 
at once to form, as soon as the stopcock is 
closed it will accumulate. If the stopcock 
be opened and a light applied to the jet, the issuing gas 
will take fire, and, on holding a piece of white porcelain 
in the flame, the arsenic will accumulate on it as a me- 
tallic ring; or the jet may be replaced by a bent tube 
of hard glass, which is to be kept heated at one point 
for a length of time. The arsenic will be detected as a 
black deposit, though it exist to an extremely minute 
extent. 

If the liquor, notwithstanding the care taken to clear 
it, froths when the hydrogen is disengaged, so as to in- 
terfere with the results by choking the tube, the gas is 
best collected under ajar at the pneumatic trough, and 
may be subsequently examined. 

The fifth test, by copper, may be sometimes advan- 
tageously applied to collect the arsenic from solutions; 
the crust upon the copper may be subsequently exam- 
ined, either by sublimation or otherwise. 

It is to be remembered that antimony will yield re- 
sults closely resembling those of arsenic by Marsh's 
test ; but on heating the glass plate on which the stain 

Describe Marsh's test. How may minute quantities be detected 
by this test ? When the liquor froths, what has to be done ? When 
is the copper test advantageously applied ? What metal acts like 
arsenic ? How is it distinguished ? 



ARSENIOUS ACID. 319 

has been deposited, if it be arsenic it will totally vola- 
tilize away ; but if antimony, it will not disappear, but 
only give rise to a yellow oxide. The antimony stain 
is readily soluble in hydrosulphate of ammonia, the ar- 
senic stain with difficulty. On evaporating, the sul- 
phide of arsenic is found to be soluble in ammonia, the 
sulphide of antimony in hydrochloric acid. 

In medico-legal investigations, it should also be re- 
membered that, as sulphuric acid and zinc of commerce 
contein arsenic, it is absolutely necessary that the speci- 
mens about to be used be critically examined themselves 
by being tried alone before the suspected solution is 
added. 



LECTURE LXV. 

Arsenic. — Antiseptic Quality of Arsenious Acid. — 
Antidote for Poisoning. — Arsenic Acid. — Isomor- 
phics toith Phosphoric Acid. — Realgar and Orpi- 
ment. — Arseniureted Hydrogen. — Antimony. — Re- 
duction of. — Oxides, Chlorides, and Sulphides of. — 
Antimoniureted Hydrogen. — Detection of Antimony. 
— Tellurium. — Copper. — Reductio?i of. — Use of Ox- 
ide. — Detection of— Salts of Protoxide. 

Arsenious Acid possesses a remarkable antiseptic 
quality, and hence often preserves the bodies of persons 
who have been poisoned by it. Advantage is also taken 
of this fact by the collectors of objects of natural histo- 
ry in preserving their specimens. 

The antidote for poisoning by arsenic is the hydrated 
sesquioxide of iron. It may be made by adding car- 
bonate of soda to the chloride of iron. It should be 
given in the moist state, mixed with water. After be- 
ing once dried it loses much of its power. It produces 
an inert basic arsenite of the peroxide of iron. 

Arsenic Acid is found in nature in union with various 
bases. It may be made by acting on arsenious acid with 
nitric acid, with the addition of a little hydrochloric acid, 
and evaporating till the nitric acid is expelled. The re- 
Why must the sulphuric acid and zinc be examined ? Of what 
use is the antiseptic quality of arsenic ? What is the antidote for 
arsenic ? How is it prepared ? How is arsenic acid prepared ? 



360 ANTIMONY. 

suiting acid contains three atoms of water, and is iso- 
morphous with tribasic phosphoric acid. The arseniates 
yield, with nitrate of silver, a dark red precipitate of the 
tribasic arseniate of silver. It should not be forgotten, 
in medico-legal inquiries respecting arsenic, that the ar- 
seniate of lime may naturally replace phosphate of lime 
in bone-earth, and this acid substitute the phosphoric in 
other parts of the system. 

H The bisulphide of arsenic may be obtained by melting 
arsenious acid with sulphur. It occurs as a mineral, 
Realgar, and is a red-colored substance. 

The tersulphide is deposited when a stream of sul- 
phureted hydrogen is passed through a solution of ar- 
senious acid. It is a yellow body, and is used in dye- 
ing ; it is also known under the name of Orpiment. 

Arseniureted Hydrogen is prepared by acting on an 
alloy of zinc and arsenic with dilute sulphuric acid. It 
is a colorless gas, burns with a blue flame, exhales an 
odor like garlic. Its specific gravity is 2.695. It is de- 
composed by chlorine and iodine, and the arsenic is sep- 
arated by heat and by the rays of the sun. 

Antimony. #5 =12 9. 

This metal occurs commonly as a sulphide in nature, 
from which it may be obtained by heating with iron 
filings, a sulphide of iron forming, and metallic antimo- 
ny subsiding to the bottom of the crucible. It may 
also be obtained by fusing the sulphide with black flux, 
which produces a sulphide of potassium and metallic 
antimony. 

Antimony is a blue- white metal, of a very crystalline 
structure, and so brittle that it may be pulverized. It 
melts at 840°. Its specific gravity is 6.7. It possesses, 
at high temperatures, an intense affinity for oxygen ; a 
fragment of it the size of a pea being ignited on a piece 
of charcoal before the blowpipe, and then suddenly 
thrown on the table, takes fire, breaking into a multi- 
tude of globules, and filling the air with fumes of the 
white teroxide. Antimony yields the following com- 
pounds : 

Where may arsenic exist in the body ? What is Realgar ? What 
is Orpiment ? How may arseniureted hydrogen be made ? How is 
metallic antimony made ? What are its properties ? 



COMPOUNDS OF ANTIMONY. 361 

Teroxide of Antimony Sb0 3 = 153 

Antimonious Acid. SbO^ =161 

Antimonic Acid Sb0 5 =169 

Terchloride of Antimony SbCl 3 =235.5 

Perchloride " SbCl 5 =306.5 

Tersulphide " SbS 3 =177 

Persulphide " SbS 5 =209 

Oxysulphide " 2Sb, S 3 +SbO 3 =507 

The Teroxide of Antimony may be made by adding 
to an acid boiling solution of chloride of antimony car- 
bonate of soda. It is a gray powder, and is the base 
of a class of salts, among which tartar emetic may be 
mentioned. These salts give an orange-colored precip- 
itate with sulphureted hydrogen. 

Antimonious Acid is produced by heating the oxide 
of antimony, or antimonic acid. It is a white powder, 
and unites with bases, forming antimonites. 

Antimonic Acid may be prepared by acting on me- 
tallic antimony with nitric acid. 

Terchloride of Antimony is made by dissolving one 
part of sulphide of antimony in five of hydrochloric 
acid, and distilling. As soon as the matter which pass- 
es over becomes solid, the receiver is to be changed, 
and, continuing the heat, the terchloride is collected. 
It was formerly known as Butter of Antimony. The 
.perchloride may be made by burning antimony in chlo- 
rine gas. The oxychloride is produced when the ter- 
chloride is placed in contact with water. It was for- 
merly known as Powder of Algaroth. 
„ The tersulphide occurs abundantly as a mineral, as 
has been said. It is also formed by the action of sul- 
phureted hydrogen on the salts of the oxide of anti- 
mony. In this case it is of an orange, color, in the for- 
mer it has a metallic aspect. The persulphide is pro- 
cured when the tersulphide and sulphur are boiled in a 
solution of potassa, the liquor filtered, and an acid add- 
ed, a yellow precipitate going down. It was known 
formerly as the Golden Sulphur et of Antimony. The 
oxysulphide occurs native as the red ore of antimony, 
and may also be made by boiling the tersulphide with 

What color does sesquioxidc of antimony yield with sulphureted 
hydrogen ? How is antimonious acid made ? How is terchloride of 
antimony made ? What is Powder of Algaroth ? What is the gold- 
en sulphuret of antimony ? 

Q 



362 ANTIMONIUBETED HYDROGEN. 

a solution of potassa. On cooling, precipitation of it 
takes place. It is stated, however, by Berzelius, that 
this is not a true compound, but merely a mechanical 
mixture of the oxide and sulphide in irregular propor- 
tions. This precipitate is also known under the name 
of Kermes Mineral From the liquor, after the kermes 
is separated, an acid throws down the golden sulphuret 
of antimony. 

Antimoniureted Hydrogen. — When hydrogen is 
evolved from a solution containing tartar emetic (tar- 
trate of antimony and potassa), this substance is pro- 
duced. It is a gas, having a superficial resemblance to 
arseniureted hydrogen, and, when used as in Marsh's 
apparatus, gives a stain on glass resembling that of ar- 
senic. From arsenic it may be distinguished by not 
being volatile. 

The following method of detecting antimony, when 
dissolved in any organic liquid, is based upon the prin- 
ciple, by which copper and other metals may be detect- 
ed under similar circumstances : Acidulate a portion 
of the suspected liquid with hydrochloric acid, and place 
it in a shallow platinum capsule. Touch the platinum 
through the acid liquid w T ith a piece of pure zinc. 
Wherever the metals come in contact, antimony in the 
state of a black powder is deposited on the surface of 
the platinum. Hydrosulphate of ammonia dissolves the 
deposit by the aid of heat, giving the orange-red sul- 
phide, which is soluble* in hydrochloric acid. 

In Marsh's test zinc causes the deposit of the anti- 
mony as a black powder, and after a short time barely 
a trace will escape with the hydrogen from the jet. 

Antimony furnishes some valuable alloys; printers' 
type metal, for example, is an alloy of this substance 
with lead. It expands in the act of solidifying, and 
therefore takes accurate impressions of the interior of a 
mould. 

Tellukium. Te=z64. 

Tellurium is a rare metal, of a white color, yery fusi- 
ble and volatile, having several analogies with selenium, 

What is kermes mineral ? How is antimoniureted hydrogen made? 
How may antimony be detected in organic liquids ? What alloys of 
antimony are there ? What are the properties of tellurium ? 



COPPER. 363 

and uniting with hydrogen to form tellureted hydro- 
gen, which, with water, yields a claret-colored solution. 

Copper. Cu=B2. 

Copper is often found native, and in certain parts of 
the United States in masses of very great magnitude. 
It also occurs as a carbonate and sulphide. In the lat- 
ter combination it is found with the sulphide of iron, as 
yellow copper ore. This being roasted, the sulphide of 
iron changes into oxide, the copper sulphide remaining 
unchanged. The mass is then heated with sand, which 
yields a silicate of iron, the sulphide of copper separa- 
ting. This process is repeated until all the iron is part- 
ed ; and now the sulphide of copper begins to change 
"into the oxide, which is finally decomposed by carbon 
at a high temperature. 

Copper is a red metal, requiring a high temperature 
for fusion, 1996°. Its specific gravity is 8.8. It has 
great tenacity, and is ductile and malleable. A polished 
plate of it, heated, exhibits rainbow colors, and is finally 
coated with the black oxide. It is one of the best con- 
ductors of heat and electricity. Among its compounds 
the following may be mentioned : 

Protoxide of Copper ,..- CuO =40 

Suboxide " Cu 2 =72 

Chloride " CuCl =67.5 

Subchloride '« Cu 2 Cl=99.5 

Subsulphide " Cu 2 S =80 

Protoxide of Copper may be made either by igniting 
metallic copper in contact with air, or by calcining the 
nitrate. It is a black substance, not decomposable by 
heat, but yielding oxygen with facility to carbon and 
hydrogen, and hence extensively used in organic analy- 
sis. It is a base, yielding salts of a blue or green color. 
The suboxide, called also red oxide, occurs native as 
ruby copper. It is a feeble base. The subsulphide also 
occurs native, as copper pyrites. 

Copper is easily detected. Caustic potassa gives, 
with its protosalt, a pale blue hydrate, which turns 
black on boiling. Ammonia, in excess, yields a beau- 

Under what forms does copper occur ? How is it reduced ? What 
are its properties ? Which oxide is used in organic analysis? How 
is copper detected ? 



364 SALTS OF COPPER. 

tiful purple solution; ferrocyanide of potassium, a choc- 
olate-brown precipitate ; sulphureted hydrogen, a black ; 
and metallic iron, as the blade of a knife, precipitates 
metallic copper. 

Salts of the Protoxide of Copper. 

Carbonate of Copper. — There are several varieties 
of carbonates. One, which passes under the name of 
Mineral Green, is formed by precipitating with an al- 
kaline carbonate. It occurs naturally in the form of 
Malachite. Blue copper ore is another carbonate ; the 
paint called Green ~Verditer has a similar composition. 

Sulphate of Copper {Blue Vitriol) is prepared for 
commerce by the oxidation of the sulphide of copper. 
It crystallizes in rhomboids of blue color, w r ith five 
atoms of water. It is soluble in four times its weight 
of cold, and twice its weight of hot water. It is an 
escharotic, an astringent, and has an acid reaction. 
With ammonia it forms a compound of a splendid blue 
color, which may be obtained in crystals ; with potassa, 
also, it forms a double salt. There are also subsulphates 
of copper. 

Nitrate of Copper, formed by the action of nitric 
acid on metallic copper. It crystallizes in prisms or in 
plates. It acts with very great energy on metallic tin. 
There is a subnitrate of copper. 

Arsenite of Copper {ScheeWs Green), produced by 
adding solution of arsenious acid to the solution of am- 
monia sulphate of copper. 

Copper yields several valuable alloys. Brass is an al- 
loy of copper and zinc ; gun metal, bell metal, and spec- 
ulum metal, of copper and tin. The gold and silver of 
currency contain portions of this metal ; it communi- 
cates to them the requisite degree of hardness. 

Under what forms does the carbonate occur? What are the 
method of preparation and properties of the sulphate ? What is 
Scheele's Green ? What alloys of copper are there ? 



LEAD. 365 



LECTURE LXVI. 

Lead. — -Reduction of Galena. — Relations of Lead to 
Water. — The Oxides of Lead. — Detection of Lead. 
— Bismuth. — Silver. — Amalgamation. — Crystalli- 
zation. — Cupellation. — Properties of Silver. — Salts 
of Silver. 

Lead. P5=104. 

Lead occurs under various mineral forms, but the 
most valuable one is galena, a sulphide. From this it 
is readily obtained. The galena, by roasting in a rever- 
beratory furnace, becomes partly converted into sul- 
phate of lead; the contents of the furnace are then 
mixed, the temperature raised, and the sulphate and 
sulphide produce sulphurous acid and metallic lead, the 
action being 

JPbO,S0 3 +RbS... = ...2S0 2 +Rb 2 . 

Lead is a soft metal, of a bluish-white color. Its spe- 
cific gravity is 11.381. It melts at 612°, and on the sur- 
face of the molten mass an oxide (dross) rapidly forms. 
At common temperatures it soon tarnishes. In the act 
of solidifying it contracts, and hence is not fit for cast- 
ings. It possesses, at common temperatures, the weld- 
ing property ; two bullets will cohere if fresh-cut sur- 
faces upon them are brought in contact. Under the 
conjoint influence of air and water lead is corroded, a 
white crust of carbonate forming ; but when there are 
contained in the water small quantities of salts, such as 
sulphates, these form with the lead insoluble bodies, 
which, coating its surface over, protect it from farther 
destruction. For this reason lead pipe can be used for 
distributing water in cities without danger. Lead is 
one of the least tenacious of the metals. The tartrate 
of lead calcined in a tube yields one of the best pyro- 
phori; on bringing it into the air at common tempera- 
tures, it spontaneously ignites. 

Under what forms does lead chiefly occur ? How is galena re- 
duced ? Why can not lead be used for castings ? What is the ac- 
tion of pure water, and water containing salts, upon it? 






36G COMPOUNDS OF LEAD. 

Of the compounds of lead, the following are some of 
the more important : 

Protoxide of Lead PbO =112 

Sesquioxide " Pb 2 3 =2S2 

Peroxide " Pb0 2 =120 

Eed oxide " P& 3 O t =344: 

Chloride " PbCl =139.5 

Iodide " Pbl =230 

Sulphide « .PbS =120 

The protoxide is made by heating lead in the air; it 
is a yellow body, which fuses at a bright red heat. In 
the first state it is called massicot ; in the latter, lith- 
arge. It yields a class of salts, being a base. It is 
slightly soluble in water. The peroxide is made from 
red lead by digesting it with nitric acid, which dis- 
solves out the protoxide, and leaves the substance as a 
puce-colored powder. The red oxide, or red lead, is 
made by calcining lead in a current of air at 600° or 
700°. It is used in the manufacture of flint glass. 
The chloride is made by the action of hot hydrochloric 
acid on protoxide of lead : on cooling, it is deposited In 
crystals. The iodide is formed when any soluble iodide 
is added to a protosalt of lead. It is a beautiful yellow 
precipitate, soluble in boiling water, forming a colorless 
solution, which, on cooling, deposits golden crystals. 
The sulphide is galena ; it crystallizes in cubes, and has 
a high metallic lustre. 

Lead is easily detected by sulphureted hydrogen, 
which throws it down from its solutions as a deep" 
brown or black precipitate, and by the iodide of potas- 
sium or chromate of potassa, which give with it a yel- 
low precipitate. Sulphuric acid yields with its salts a 
white insoluble sulphate of lead. 

Salts of the Protoxide of Lead. 

Carbonate of Lead — White Lead — Ceruse. — This 
salt forms as a white precipitate when an alkaline car- 
bonate is added to a solution of a salt of lead. Large 
quantities of it are consumed in the arts as white paint. 
For commerce it is procured by mixing litharge with 
water containing a small proportion of acetate of lead ; 

What are massicot and litharge ? What is red lead ? How is 
lead detected ? How may white lead be made ? 



BISMUTH. 367 

carbonic acid gas is then sent over it, and the carbonate 
rapidly forms. It is also made by exposing metallic 
lead in plates to the action of the vapor of vinegar, air, 
and moisture, the metal becoming oxidized and carbon- 
ated. 

Nitrate of Lead may be formed by dissolving litharge 
in dilute nitric acid. It crystallizes in opaque white oc- 
tahedrons, which dissolve in seven or eight times their 
weight of cold water. They contain no water of crys- 
tallization, and are decomposed at a red heat, as stated 
in the description of nitrous acid. By the action of am- 
monia three other nitrates of lead may be obtained. 

Among the alloys of lead are the soft solders. Two 
parts of lead and one of tin constitute plumber's solder ; 
one of lead and two of tin, fine solder. 

Bismuth. jBfe213. 

Bismuth is found both native and as a sulphide. It 
is of a reddish color, melts at 507°, and may be obtained 
in beautiful cubic crystals by cooling a quantity of it un- 
til solidification commences, then breaking the surface 
crust and pouring out the fluid portion. 

When bismuth is dissolved in nitric acid, and the so- 
lution poured into water, the white subnitrate, once used 
as a cosmetic, is deposited; when this is washed, and 
subsequently heated, the protoxide is left. There is also 
a peroxide. 

Fusible metal is an alloy of eight parts of bismuth, 
five of lead, and three of tin. It melts below the boil- 
ing point of water, and may be obtained in crystals. 

Silver. .4^=108. 

Silver is found native, and as a sulphide and a chlo- 
ride, occurring also with a variety of other metals, and 
in small proportion with galena. When disseminated 
as a metal through ores, it may be collected from them 
by amalgamation with quicksilver; on distilling, the 
quicksilver is driven off. 

When it is obtained from the sulphide, that ore is 
roasted with common salt, which changes it into a 

What are the properties of the nitrate ? What are solders ? What 
are the properties of bismuth ? What is fusible metal ? Under what 
forms does silver occur ? How is it obtained from the sulphide ? 



368 SILVER, 

chloride. This, with the impurities with which it may- 
be associated, is put into barrels, which revolve on an 
axis, along with water, pieces of iron, and metallic mer- 
cury ; the iron reduces the chloride to the metallic state, 
and the silver amalgamates with the mercury. This is 
washed from the impurities, strained through a bag to 
separate the excess of mercury, and the residue is driv- 
en off by distillation. 

The extraction of silver, when it octurs in small quan- 
tity with lead, is accomplished by the process of crys- 
tallization. It depends upon the fact that an alloy of 
lead and silver is more fusible than lead. A large quan- 
tity of argentiferous lead is melted and allowed to cool. 
As the setting goes on, the first portions which solidify 
are pure lead ; they may be removed by iron colanders, 
and by continuing the process there is finally left a por- 
tion containing all the silver. This is exposed to a red 
heat, and a stream of air directed over it ; oxidation of 
the lead takes place, and the litharge is removed by the 
blast, the process being finally completed by cupella- 
tion. 

A cupel is a shallow dish made of bone ashes, and is 
very porous. In this, if an alloy of lead and silver be 
heated with access of air, the lead oxidizes, and, melting 
into a glass, soaks into the cupel, or may be driven from 
the surface by a blast of air directed from a bellow r s. 
At the same time, any copper or other base metal oxi- 
dizes and is removed along with the lead. The com- 
pletion of the process is indicated by the silver assum- 
ing a certain brilliancy, or flashing, as the workmen 
term it. 

Silver is a w r hite metal, capable of receiving a brilliant 
polish. It is malleable and ductile, an excellent con- 
ductor of heat and electricity. Its specific gravity is 
10.5. It melts at 1873°, and when melted absorbs a 
large quantity of oxygen, giving it out again as soon as 
it solidifies, and assuming a frosted or porous appear- 
ance. The presence of a minute quantity of copper pre- 
vents this effect. Silver is so soft that, for making plate 
or coins, it requires to be alloyed with a portion of cop- 

What is the process of amalgamation ? What is the process of 
crystallization ? What is cupellation ? What are the properties of 
silver ? When must it be alloyed ? 



COMPOUNDS OF SILVER. 369 

per ; from this it may be purified by dissolving it in ni- 
tric acid, and precipitating the silver as chloride by a 
solution of common salt. Silver shows little disposition 
to unite with oxygen, though it tarnishes readily by the 
action of sulphureted hydrogen. It yields three oxides, 
but of its compounds the following are the most im- 
portant : 

Protoxide of Silver AgO =116 

Chloride " ,.AgCl=U3.5 

Iodide " Agl =234 

Sulphide " AgS =124 

The protoxide may be made by the action of caustic 
potassa on a solution of nitrate of silver, or by boiling 
recently -prepared chloride in potassa. It is a dark 
powder, which may be reduced by heat alone. The 
chloride is sometimes found native, as horn-silver, and 
may be made by precipitation from the nitrate by hy- 
drochloric acid or a soluble chloride. The sulphide is 
produced whenever sulphureted hydrogen acts on oxide 
of silver, or even metallic silver ; it is a black compound. 

Silver is easily detected by precipitation as a chlo- 
ride : a curdy, white precipitate, insoluble in water, but 
soluble in ammonia. It turns dark on exposure to the 
sun, and is used in photography. The iodide and bro- 
mide of silver are very valuable in being sensitive to 
light. They are formed in that application by dipping 
a film of collodion containing some soluble iodide and 
bromide into a solution of nitrate of silver. They also 
exist native in Mexico. 

Salts of the Peotoxide of Silver. 

Nitrate of Silver {Lunar Caustic), procured by dis- 
solving silver in nitric acid diluted with twice its weight 
of water. It crystallizes in tables, which are not deli- 
quescent, and contain no water of crystallization 1 ? It en- 
ters into fusion at 426°, but at higher temperatures un- 
dergoes decomposition. It is frequently cast into small 
sticks, and used by surgeons as a cautery. It is soluble 
in its own weight of cold and half its weight of hot wa- 

• How may the protoxide be made? What special properties have 
the chloride, iodide, and bromide ? How may silver be detected ? 
How is lunar caustic made ? What properties* has it? 

Q2 



370 COMPOUNDS OF SILVEE. 

ter, and, when in contact with organic matter, turns 
black in the rays of the sun. 

Ammoniuret of Silver {JBerthollefs Fulminating 
Silver) is formed by digesting precipitated oxide of 
silver in ammonia. It explodes with the utmost vio- 
lence under the feeblest friction, with the evolution of 
nitrogen and the vapor of water. 

Hyposulphite of Silver is formed when a compound 
of silver is dissolved in any of the hyposulphites. The 
solution of chloride of silver has a sweet taste, as may 
be observed when removing the excess of chloride from 
paper that has been used in the positive printing pro- 
cess. 

Ammonia Nitrate of Silver, formed by adding am- 
monia to nitrate of silver till the precipitate at first 
formed is redissolved, is employed in photographic 
printing on paper. 

Silvering a glass is performed by various processes, 
the best being that in which a solution of nitrate of sil- 
ver and ammonia is decomposed by Rochelle salt. The 
film deposited on glass is so hard as to bear polishing 
with buckskin, though only 2o~oyooo* °f an i ncn thick. 
This process has been largely used by the author in 
making the 15j-inch silvered glass reflectors for his tel- 
escope at Hastings-on-Hudson, New York. It is fully 
described in the Contributions to Science of the Smith- 
sonian Institution for 1864. 

Brass may be silvered by the aid of chloride of silver, 
chalk, and carbonate of potassa. In electro-plating a so- 
lution of the chloride in cyanide of potassium is used. 

What is ammoniuret of silver ? "What are the properties of the 
hyposulphite ? Of what use is the ammonia nitrate ? How is sil- 
vering on glass performed? How may brass be silvered ? 



MERCURY. 371 



LECTURE LXVII. 

Mercury. — Process of Reduction. — The Liquid State 
of. — Its Oxides. — Calomel and Corrosive Sublimate. 
— Detection of Mercury.— Its Salts. — Amalgams. — 
Gold. — Chloride of. — Purple of Cassius. — Palla- 
dium. — Platinum. — Its Catalytic Effects. — Plati- 
num Black.— Iridium.— Rhodium. — Ruthenium. — 
Osmium. 

Mercury. Hg=100. 
Mercury may be obtained from the sulphide (cinna- 
bar) by distillation with iron filings. It is also, to a 
certain extent, found native. 

The striking characteristic of mercury is its liquid 
condition. Its melting point is the lowest of that of 
any of the metals, being —39°. Its specific gravity at 
47° is 13.545. It boils at 662°. Kept at that tempera- 
ture in the air for a length of time, it produces red ox- 
ide, but at common temperatures it is not acted on by 
the air. It may be freed from impurities for the pur- 
poses of the laboratory by being kept in contact with 
. dilute nitric acid. It gives the following compounds of 
interest : 

Suboxide of Mercury Hg 2 =208 

Protoxide " HgO =108 

Subchloride " Hg 2 CZ=23o.5 

Chloride " HgCl =135.5 

Subsulphide " Hg 2 S =216 

Sulphide " HgS =116 

The suboxide may be made by triturating calomel 
with potassa water in a mortar. It is a black powder, 
which is decomposed by light or any of the reducing 
agents. The protoxide may be formed, as stated above, 
by the action of air on hot mercury, but more easily by 
dissolving mercury in nitric acid, and evaporating and 
heating the salt until no more fumes of nitrous acid are 
evolved. It is a red powder, and when warmed be- 
Under what forms does mercury occur ? What are the most strik- 
ing properties of this metal ? How may it be purified ? What are 
the properties of the protoxide ? 



372 COMPOUNDS OF MERCURY. 

comes almost black, the color returning as the temper- 
ature descends. Like the former, it is a base, and yields 
a class of salts. 

The Subchloride, or Calomel, may be made by add- 
ing hydrochloric acid to the subnitrate of mercury, or 
by subliming a mixture of chloride of mercury and mer- 
cury. It is a white powder, insoluble in water, and 
darkens slowly by exposure to sunshine. The chloride 
(or Corrosive Sublimate) is formed when mercury burns 
in chlorine gas, but more economically by sublimation 
from a mixture of sulphate of mercury and common 
salt. It is a heavy, white, crystalline body, soluble in 
water, has a metallic taste, and is poisonous. The an- 
tidote for'it is albumen (the white of egg). 

Of the sulphides of mercury, the subsulphide is black 
and the sulphide commonly red; in this case it passes 
in commerce under the name of vermilion, and is used 
as a paint. It can be obtained, however, quite black ; a 
similar double color is observed in the case of the ox- 
ide, and still more strikingly in the iodide, which may 
be sublimed in beautiful yellow crystals, becoming of a 
splendid scarlet color by merely being touched. 

Mercury may be detected by being precipitated from 
its soluble combinations by metallic copper as a metal. 
Its salts, either alone or with carbonate of soda, heated 
in a tube, yield metallic mercury, which volatilizes. 

Salts of the Oxides of Mercury. 

Nitrates of the Oxides of Mercury. — When cold di- 
lute nitric acid acts on mercury it gives rise to neutral 
or basic subsalts, as the acid or mercury is in excess; 
if the acid be hot, a pernitrate forms ; these salts are 
decomposed by an excess of water, giving rise to basic 
compounds. 

Sulphate of Mercury is formed by boiling sulphuric 
acid and mercury, and evaporating to dryness. It oc- 
curs in the form of a white granular mass, and is decom- 
posed by water, giving a yellow precipitate, a subsul- 
phate called Turpeih Mineral. 

How may calomel be made? When is corrosive sublimate form- 
ed ? What is its antidote ? What is vermilion? What is the pe- 
culiarity of the iodide ? How is mercury detected ? What is Tur- 
peth Mineral ? 



GOLD. PALLADIUM. 373 

The alloys of mercury are called amalgams ; the 
amalgam of tin is used for silvering looking-glasses, and 
that of zinc for exciting electrical machines. 

Gold. Au=I97. 

Gold is found native, and may be obtained by wash- 
ing or by amalgamation with mercury. It may be pu- 
rified from silver by quartation ; that is, fusing it with 
three times its weight of silver, and then acting on the 
mass with nitric acid. The gold is left as a dark pow- 
der. 

From other metals gold is distinguished by its yellow 
color. Its specific gravity is 19.3. It melts at 2016°. 
It is the most malleable of all the metals, as is proved 
by gold leaf, which may be obtained wovoiro i ncn i* 1 
thickness ; is not acted upon by the air or oxygen. Ob- 
jects of art covered with it have retained their brillian- 
cy for thousands of years. No acid alone dissolves it, 
but it is soluble in aqua regia, and also in chlorine. 

It can, however, be made to yield two oxides, a pro- 
toxide and a teroxide; and two chlorides having the 
same constitution ; the terchloride is formed by the ac- 
tion of nitromuriatic acid (aqua regia) on gold. When 
evaporated, it yields red, deliquescent crystals. Deox- 
idizing agents, such as protosulphate of iron, reduce it 
to the metallic state ; this is probably due to their de- 
composing water and presenting hydrogen to the chlo- 
ride. Hydrogen gas decomposes the terchloride, and, 
by heating, it first changes into the protochloride and 
then into metallic gold. With a solution of tin it forms 
the Purple of Cassius. This and the action of proto- 
sulphate of iron serve as a test for it. 

Palladium. JPJ— 5 4 . 
Palladium is found associated with platinum, and is 
best obtained from the cyanide of palladium by ignition. 
It is a white metal, requiring a high temperature for fu- 
sion; specific gravity 11.5. It does not tarnish in the 
air, is dissolved by nitric acid and aqua regia, is one of 

What are amalgams ? How does gold occur ? What is quarta- 
tion ? What are the properties of gold ? How many oxides has it ? 
What are the tests for it? What is the Purple of Cassius? With 
what metal is palladium found ? What are its properties ? 



374 PLATINUM. 

the welding metals, and, when heated, acquires a purple 
oxidation like watch-spring. It is used to some extent 
by dentists. Its compounds are not of importance, with 
the exception of the protochlori.de, which I have shown 
to be useful in increasing the opacity of under-exposed 
negatives. It increases their intensity 16 times, with- 
out any liability to staining or injury. 

Platinum. Ptf=99. 

Platinum is found native, but always associated with 
other metals. It may be obtained by first forming a 
chloride of platinum and ammonium; this, when ignited, 
leaves pure spongy platinum, which being exposed to 
powerful pressure, and then alternately made white-hot 
and hammered, becomes a solid mass. 

Platinum is a white metal. Its specific gravity is 
very high, being 21.15. Malleable platinum is manufac- 
tured by Deville's process as follows, 230 pounds hav- 
ing been fused in one mass. The platinum ore is fused 
with its weight of sulphide of lead and half its weight 
of metallic lead. Some of the impurities are thus sep- 
arated in combination with sulphur, while the platinum 
forms an alloy with the lead, which is freed from the 
scoriae, and subjected to the joint action of heat and air 
until all but about five per cent, of the lead is oxidized. 
It is then subjected to the intense heat of an oxyhydro- 
gen flame in a furnace of chalk-lime, where the rest of 
the lead, together with any gold, copper, and osmium, is 
driven off in fumes. Rhodium and iridium are left in 
combination. 

Platinum is a welding metal, and on this fact the first- 
mentioned method of preparation depends. It is very 
malleable and ductile, is not acted upon by oxygen, air, 
or any acid alone, but dissolves in aqua regia. It pos- 
sesses the extraordinary property of causing hydrogen 
and oxygen to unite at common temperatures, an effect 
which takes place with remarkable energy when the 
metal is in a spongy state. A jet of hydrogen falling 
upon spongy platinum in the air makes it red-hot, and 

Of what value is the protochloride ? How is platinum obtained 
from its ores ? What is its specific gravity ? What is Deville's pro- 
cess ? What fluid dissolves platinum ? What relation does it bear 
to hydrogen ? 




IRIDIUM. RHODIUM. 375 

presently after the gas takes fire. It also brings about 
the rapid transformation of alcohol into acetic acid, and 
various other chemical changes. 

If a quantity of ether be poured Fig.m. 

into a glass jar, Fig, 291, and a coil 
of platinum wire, recently ignited, be 
introduced, the metal continues to 
glow so long as any ether is present. 

Platinum is invaluable to the chem- 
ist. It furnishes a variety of imple- 
ments of great value, and is met with 
under the forms of crucibles, tubes, 
wire, foil, etc. m 

Platinum Black is prepared by "% 
slowly heating to 212° a solution of 
chloride of platinum, to which an excess of carbonate 
of soda and some sugar have been added. It is a dark 
powder, and possesses the property of determining a 
variety of chemical changes with much more energy 
than platinum in mass. 

Platinum can be caused to yield two oxides, which 
are not of any importance ; and two analogous chlo- 
rides, of which the bichloride, which is the common pla- 
tinum salt, is made by dissolving the metal in nitrohy- 
drochloric acid, and evaporating to a sirup. It is solu- 
ble in water and alcohol, and is used for detecting the 
salts of potassium, rubidium, and caesium, which give 
compounds insoluble in alcohol and almost so in water. 

Iridium. It— 99. 
Iridium is associated with platinum. It is said to 
have been found of specific gravity 26. Dr. Hare ob- 
tained it 21.8; it is therefore the heaviest of the metals. 
Its name is derived from the different colors (iris) of its 
compounds.' 

Rhodium. H=52. 
Like the former metal, rhodium is associated with the 
platinum ores. It is a hard white metal; its specific 
gravity is 11, and is sometimes used to form tips to 
metallic pens. 

Describe the flameless lamp. What is platinum black ? Of what 
use is bichloride of platinum ? What are the properties of iridium ? 
of rhodium ? 



376 



RUTHENIUM. OSMIUM. 



Ruthenium. Mu—52. 
This is one of the metals remaining in that portion of 
.the ore of platinum which resists the action of aqua re- 
gia. It is hard, brittle, infusible in the oxyhydrogen 
flame, but readily oxidized by fusion with nitre, furnish- 
ing four oxides. 

Osmium. 05 = 100. 
Obtained by precipitation, it is in the form of a black 
powder, which acquires a metallic lustre by friction. 
The specific gravity slightly exceeds that of platinum. 
Burned in the air, it oxidizes, exhaling poisonous fumes; 
hence its name (os?ne, odor). It forms five oxides. 

There are some peculiarities belonging to the six pre- 
ceding metals — namely, platinum and its associates — 
which deserve notice in reference to their atomic weights 
and specific gravities, and which have led to their divis- 
ion into two groups of three each : 



Sp.Gr. At.W't. 

Platinum 21.15 99 

Iridium 21.80 99 

Osmium 21.40 100 



Sp. Gr. At.W't. 

Palladium 11.8 54 

Rhodium 12.0 52 

Ruthenium 11.3 52' 



It will be observed that the specific gravities -and 
atomic weights of the first group are almost identical ; 
so also are those of the second group ; and in the latter 
case they are almost exactly one half of those in the 
former. 

What are the properties of ruthenium ? of osmium ? What pecu- 
liarities belong to the six preceding metals ? 



PART IV. 

ORGANIC CHEMISTRY. 



LECTURE LXVIXI. 

Composition of Organic Bodies. — Their Pr oneness to 
Decomposition. — Formulas of Organic Substances. 
— The Compound JRadical Theory. — Theory of Types 
and Law of Equivalent Substitution. — Examples of 
Suhstitutio7is. — Homologous Compounds. — Action of 
Seat. — Eremacausis. — Putrefaction. — Difficulties in 
the Nomenclature of Organic Bodies. 

Oeganic Chemistry, which treats of the substances 
derived from the processes of life and the compounds 
that arise from them, has been defined as the chemistry 
of the compounds of carbon, because all such bodies, 
with a few exceptions, as ammonia, contain that ele- 
ment, and are more or less combustible. Three other 
'elements, hydrogen, nitrogen, and oxygen, also enter 
largely into their constitution, while potassa, soda, lime, 
magnesia, iron, arsenic, chlorine, fluorine, sulphur, phos- 
phorus, silica, etc., are found to a limited extent, or may 
be made artificially to become components of them. 
The variety in the nature of substances which distin- 
guishes inorganic chemistry is here replaced by a va- 
riety resulting from the varied groupings of a few ele- 
ments. 

The atomic constitution of organic substances is much 
mare complex than that of inorganic ; fibrin, for exam- 
ple, is regarded as having the formula 

^216-^169^68-^27^25 

four hundred and eighty-two atoms entering into the 
composition of one of its atoms; while soda and potas- 
sa consist of only two atoms, carbonic acid of three, 

What is the definition of organic chemistry ? What elements en- 
ter into organic bodies ? What is the constitution of fibrin ? 



378 COMPOSITION OF ORGANIC SUBSTANCES. 

sulphuric acid of four, etc. As a consequence of this 
complexity, organic substances exhibit a great prone- 
ness to decomposition, very slight causes sufficing to 
break down their constitution by destroying the bal- 
ance of affinities, and give origin to simpler and more 
stable compounds. In the bodies of animals the prod- 
ucts of oxidation and metamorphosis of nitrogenized 
substances have continually to be removed by the pro- 
cess of secretion for a healthy condition to be maintain- 
ed. As soon as death ensues a general decomposition 
sets in, and in a short time the tissues are resolved into 
a few simple substances — water, ammonia, carbonic acid, 
etc. At the same time, the force which was locked up 
in them is liberated generally in the form of heat. Be- 
fore these products can again become organized, a fresh 
supply of force must be furnished from the sun; the 
carbon of carbonic acid can not again enter as a constit- 
uent into gum, or albumen, or fibrin, unless under the 
influence of the yellow ray of light. In this respect the 
vegetable and animal kingdoms stand in a position of 
antagonism or counterpoise to one another, plants or- 
ganizing food for animals, and they, in turn, oxidizing 
organized products so as to be suitable for the suste- 
nance of plants. 

Many organic substances, which yield, on analysis, pre- 
cisely the same percentage amounts of their ingredients^ 
have yet properties altogether distinct. In order to ac- 
count for such distinctions, chemists have been forced to 
the conclusion that the nature of a body does not de- 
pend alone on its constituent elements nor their relative 
amounts, but on the varied manner in which a large 
number of atoms may arrange themselves. This is 
termed Grouping. The different allotropic states that 
the combining substances may on different occasions 
present also influence the result (Lecture XXXVII.). 

When the formula of an organic substance merely ex- 
presses the number of atoms of each element present in 
it, it is called empirical ; if, on the contrary, the formu- 

What occurs to organized products in the bodies of animals? 
What takes place after death ? Whence does the force Stored up in 
vegetable products come? Are substances having the same percent- 
age amount of ingredients identical? What is meant by grouping? 
What is the difference between an empirical and a rational formula? 



THE COMPOUND RADICAL THEORY. 



379. 



la professes to show the actual arrangement of the at- 
oms, it is called rational. Thus alcohol has the empirical 
formula C 4 IT 6 2 ; its rational formula is (C\IT 5 ) O+IIO^ 
if it be regarded as the hydrated oxide of ethyle on the 
compound radical theory. 

The Compound Radical Theory. — The compound 
radical theory assumes that in organic chemistry cer- 
tain groups of atoms play the part that elements do in 
inorganic chemistry. A compound radical is therefore 
a body which combines like an element with elementary 
bodies or with other compound radicals. Some of these 
radicals have been isolated, as, for example, cyanogen 
(Cy^), but most of them have only a hypothetical ex- 
istence. This view of the constitution of organic com- 
pounds has many advantages, and greatly facilitates 
classification. The following table indicates the princi- 
pal compound radicals : 



Table of 


Compound Radicals. 


Amide. 


Salicyle. 


Propionyle. 


Carbonic Oxide. 


Cinnamyle. 


Butyle. 


Cyanogen. 


Guiacyle. 


Butyryle. 


Ferrocyanogen. 


Ethyle. 


Valeryle. 


Ferridcya'nogen . 


Acetyle. 


Caprotyle. 


Cobaltocyanogen . 


Kakodyle. 


(Enanthyle 


Chromocyanogen. 


Methyle. 


Octyle. 


Platinocyanogen. 


Formyle. 


Caproyle. 


Iridiocyanogen. 


Cetyle. 


Nonyle. 


Sulphocyanogen. 


Amyle. 


Pelargyle. 


Mellon e. ' 


Glyceryle. 


Kutyle. 


Uryle. 


Propyle. 


Palmityle. 


Benzovle. 







Some of these discharge the duties of electro-nega- 
tive, some of electro-positive, and some of indifferent 
bodies. 

The Theory of Types. — In the theory of types and 
law of equivalent substitution substances are divided 
into classes, and from each class one member is selected 
as the type. From its formula those of all the rest are 
derived by substituting for one or more of its atoms, 
atoms of other elementary substances, or else groups 
of atoms. 

What is the compound radical theory? Are these radicals hypo- 
thetical? Name the principal compound radicals. What is the 
theory of types ? 



*380 THE THEORY OF TYPES. 

As an example of such a type, we may take water 
arising from the union of one atom of hydrogen with 
one of oxygen. Its atom of oxygen may be replaced 
by one of chlorine or one of iodine, or by a compound 
radical such &s cyanogen, and thus successive classes of 
the original type arise. Types submitted to substitu- 
tion yield, therefore, different classes or forms. 

These substitutions are not necessarily restricted to 
one of the constituents ; thus, in the chloride of sodium, 
JSTaGlj we may replace the metal by potassium, calcium, 
etc. ; or we may replace the chlorine by iodine, bro- 
mine, or cyanogen, the type in both instances being still 
preserved. 

Instead of the type of water, we may examine the 
type of ammonia, which is of very frequent occurrence 
in organic chemistry. It is to be remarked that in the 
substitution of one element for another, it is not neces- 
sary that they should be of the same electro-chemical 
character; thus electro-positive hydrogen may be sub- 
stituted by electro-negative chlorine or oxygen. 

The following table exhibits instances of substitution 
in the ammonia type, the compounds being ammonias, 
that is, bases bearing an analogy to ammonia ; the salts 
are strictly analogous. 

s ) 

Type, H \ N— Ammonia. 

Ethylamine. Diethylamine. Triethylamine. 

HAN c^hAjst g.hAn 

B) H) C\H 5 ) 

Substitutions are distinguished as partial and com- 
plete. Of the former, the substitution of hydrogen by 
chlorine in Dutch liquid is an example : 

Dutch liquid, C±H 4 Cl 2 = ( C±H A ) CI 2 
1st substitution, O^H 3 CI 3 =(C 4 \ ri])Cl 2 

Give an illustration from the type of water ; from the chloride of 
sodium. What must be the electro-chemical character of the sub- 
stituted element ? Give an example of substitution in the ammonia 
type. Give an explanation of the substitutions in Dutch liquid. 



LAW OF HOMOLOGOUS SERIES. 381 

2d substitution, C±H 2 Cl±=(c\\ c f)Cl 2 

3d « C,ITCl 5 =(C 4 \^Cl 2 

4th " C\Cl 6 =(C,Ch)Cl 2 

In complete substitution, the displacement, as the 
term indicates, is immediate and total. 

The doctrine of compound radicals and that of sub- 
stitution have been regarded as being inconsistent with 
each other. There can be no doubt that the latter fa- 
cilitates the study of organic chemistry very much ; but 
there can also be no doubt of the actual existence of 
many compound radicals, since they have been isolated 
or obtained in a separate state. 

The Law of Homologous Series.— A series of com- 
pounds is homologous when each member differs from 
the others by a definite number of equivalents of carbon 
and hydrogen, or by some multiple of it; and when the 
properties of these compounds, though they may be 
similar, differ in degree from each other. The boiling 
points, as well as the specific gravities, may rise gradu- 
ally, or the compounds may gradually turn from the 
liquid into the solid condition. The following example 
is an illustration of homology : 

Formic Acid „ C 2 H 2 0^ 

Acetic " CJI±0± 

Propionic " C.H.O^ 

Butyric " C,H 8 0^ 

Valerianic " C, Q H lQ 0± 

Palmitic " C 32 i7 32 4 

Stearic " .... ....C 36 H 36 0^ 

There is an anology between homologous groups of 
organic compounds and certain groups of elementary 
bodies. For instance, chlorine, bromine, and iodine dif- 
fer from one another precisely as any three continuous 
homologous compounds might do. Chlorine is an easi- 
ly-condensible gas, bromine a volatile liquid, iodine a 
volatile solid. In affinity, bromine is intermediate be- 
tween the other two, as it is likewise in atomic weight. 

Are the compound radical theory and that of types inconsistent ? 
.When is a series homologous? Give an example of homology. 
What analogy is there between homologous groups and certain ele- 
ments? 



882 COMBINATION OF ORGANIC COMPOUNDS. 

The conclusion has been drawn, therefore, that bromine 
is made up of half an atom of each of the other two, and 
is therefore a compound body. It is curious that such 
considerations connected with the obscurer facts of chem- 
istry bring us back to the ancient doctrine of transmu- 
tation spoken of in Lecture I. If an atom of chlorine 
and one of iodine may be considered as capable of orig- 
inating two atoms of bromine, the discovery of a metal 
homologous with gold, as sodium is with potassium and 
lithium, would lead to the expectation that that metal 
might be transmuted into gold. 

From this point it w r ould appear that such substances 
as chlorine, bromine, and iodine are not to be regarded 
as elementary bodies, but as homologous compounds, 
having a common difference between them, just as is the 
case between formic, acetic, and propionic acids in the 
last table. 

Combination of organic compounds it was supposed 
can only be produced by the agency of the vital princi- 
ple, as manifested in animals or plants ; but instances are 
now accumulating which demonstrate that that opinion 
can no longer be maintained. Thus "urea may be made 
artificially by warming a solution of cyanate of ammo- 
nia ; formic acid may be prepared from carbonic oxide ; 
and from the formiates so resulting, marsh gas, defiant 
gas, and propylene may be obtained ; propylene may be 
converted into glycerine, the proximate principle of 
fats, and from glycerine a variety of sugar may be pro- 
duced. 

Organic compounds, by reason of their complex con- 
stitution, are, as has been said, prone to break up into 
subordinate groups, and eventually into binary bodies, 
carbonic acid, water, and ammonia. A slight elevation of 
temperature is often sufficient to establish these changes 
both in the absence and in the presence of air. Thus 
the decay of wood and the turning sour of wine occur. 
Where the temperature is higher with the copious ac- 
cess of air, the change promptly goes on to its last re- 
sult, the carbon finally passing into the condition of car- 

What bearing have these facts on transmutation? What view 
may be taken of iodine, bromine, and chlorine ? How may organic 
compounds be artificially produced ? Give examples. What effect 
has temperature on organic compounds? 



DESTRUCTION OF ORGANIC COMPOUNDS. 883 

bonic acid, the hydrogen into water, and the nitrogen 
escaping as free gas. To the slower change the title of 
eremacausis has been given, to the more active combus- 
tion. I^To organic substance can withstand a red heat, 
even in the absence of the air, without being totally de- 
stroyed. 

When an organic substance is undergoing slow 
changes, and is brought in contact with another capa- 
ble of being similarly affected, this last may become 
involved in the decomposition. Thus, when yeast, a 
changing nitrogenized body, is diffused through a solu- 
tion of sugar, the sugar atom is divided into carbonic 
acid and alcohol, fermentation, as it is termed, taking 
place. In like manner, putrescent animal material will 
rapidly bring on the putrefaction of fresh animal sub- 
stance. 

Both acids and bases are prone to produce change in 
organic compounds. The preparation of carbonic ox- 
ide by the action of sulphuric acid on oxalic, described 
in Lecture LIV., is an example of the former, and that 
of baryta on the acetate of potassa in the production of 
marsh gas an instance of the latter. 

From what has been said respecting the complex con- 
stitution of organic bodies, it will be inferred that their 
classification and nomenclature are attended with very 
great difficulties. An example of the attempts to indi- 
cate the constitution of these substances, not only so far 
as their grouping is concerned, but also in translating 
their formula into language, will satisfy the reader of 
the difficulty, if not impossibility, of rendering such at- 
tempts available for use. 

Thus, C^H x ^N b is called dicyanomelaniline ; and 
C^H^N, O, HO, that is, NMeAeAylPh 0, HO is call- 
ed methylethylamylophenylium. 

The arrangement of organic bodies that I shall follow 
is therefore employed rather from its usefulness than 
from its scientific propriety. 

What are eremacausis and combustion ? What is fermentation ? 
How may putrefaction be produced? Give instances of the action 
of acids and bases on organic compounds. What difficulties are 
there with the nomenclature of organic bodies? Give examples. 



384 ORGANIC ANALYSIS. 



LECTURE LXIX. 

Analysis of Organic Substances. — Proximate and 
Ultimate Analysis. — Qualitative and Quantitative 
Analysis. — Processes of Quantitative Analysis. — 
Description of Instruments. — Dialysis. — Crystal- 
loids and Colloids. 

Organic analysis may be either proximate or ulti- 
mate. Blood, for example, analyzed proximately, con- 
sists of water, fibrin, albumen, disks, etc., while its ulti- 
mate ingredients are carbon, hydrogen, nitrogen, etc. 

Ultimate organic analysis may be qualitative or quan- 
titative. In the former, where the nature of the ingre- 
dients alone is required, a few simple processes only are 
necessary. The presence of carbon is ascertained by 
the charring or blackening produced by heat or sulphuric 
acid ; that of nitrogen by the smell resembling burning 
hair when raised to a high temperature. Less quanti- 
ties of nitrogen are detected by the formation of ammo- 
nia when the substance is boiled in a solution of caustic 
potassa. Compounds containing sulphur are oxidized 
by carbonate of soda and nitrate of potassa at a melting 
heat, and the sulphuric acid produced precipitated as 
sulphate of baryta. The same treatment is used for 
phosphorus, the phosphoric acid being tested for with 
per chloride of iron and acetate of soda, or with molyb- 
date of ammonia. Inorganic substances are first pro- 
cured as ash by ignition on platinum, and then tested 
as usual in inorganic chemistry. 

Quantitative Organic Analysis is theoretically simple, 
but, on account of the many precautions necessary to 
avoid loss, and the accuracy required to detect the mi- 
nute differences in composition, is practically difficult. 

In the determination of a compound which contains 
carbon, hydrogen, and oxygen, or only the first two, the 
object is to oxidize them completely, and, weighing the 

What is meant by a proximate and what by an ultimate analysis ? 
How is the presence of carbon, nitrogen, sulplnir, phosphorus detect- 
ed ? Why is quantitative analysis difficult ? How is the analysis of 
a compound containing carbon and hydrogen conducted ? 



THE COMBUSTION-TUBE. 385 

carbon as carbonic aicd and the hydrogen as water, to 
estimate the oxygen by the loss, if there be any. This 
oxidation is accomplished by mixing the finely-powder- 
ed body with oxide of copper or chromate of lead, sub- 
stances readily yielding up their oxygen, and subjecting 
the whole to heat in a tube closed at one end and com- 
municating by the other with appropriate reagents. 
The steps of the process will be most easily understood 
by an example. The analysis of sugar is conducted as 
follows : 

A crystallized variety of sugar being selected and 
finely 'powdered, is dried at 212° by the aid of a water- 
bath, which consists of a cubical chamber surrounded 
on five sides by boiling water, and with a current of 
air passing continually through it. 

The combustion-tube in which the oxidation is effect- 
ea is made of hard glass, shaped as in Fig. 292, the 




pointed end or beak being closed. It is a foot or eight- 
een inches long, and less than half an inch in diameter. 
A sufficient supply of oxide of copper to fill it is raised 
to a red heat in a crucible to expel moisture and then 
allowed to cool. The tube from c to the beak is filled 
with oxide, from b to c with the oxide ground in a 
warm mortar with a weighed quantity (about five 
grains) of the sugar, and from a to b with oxide. Qn 
shaking the tube while in a horizontal position, the con- 
tents settle sufficiently to leave a free passage for the 
evolved gases from one end to the other. 

The contents of the tube are freed from any moisture 
that may have accumulated in them by the apparatus 
Fig. 293. D is a wooden trough, C the combustion- 
tube, B a tube containing chloride of calcium. The 
trough is filled with hot sand, as seen below, and the 
air exhausted from b and C by the syringe. A fresh 
supply of air is admitted by the stopcock a. The air 

In the examination of sugar what is the first step ? Describe the 
combustion-tube. How is it filled ? What is the use of the appara- 
tus Fig. 293? 

R 



386 



THE COMBUSTION-FURNACE. 
^ Fig. 293. 




is dried by the chloride of calcium before reaching C- 
This, in its turn, is pumped out, and the process is re- 
peated ten or twelve times. 

T]he next operation is the combustion. This is con- 
ducted by the aid of charcoal in a sheet-iron case called 
a Liebig's combustion-furnace, Fig. 294. The bottom 



Fin. 294. 




of the case is perforated to admit a draught of air, and 
from it rise a number of supports of iron to sustain the 
combustion-tube. As the whole length of the tube is 
not to be heated at once, a movable screen of sheet-iron 
has also to be provided. 

How is the combustion-furnace constructed ? 



COMBUSTION OF AN ORGANIC BODY. 387 

The entire arrangement for combustion put together 
is seen in Fig. 295 : a is the combustion-tube, b B a 



Fig. 295. 




weighed tube containing chloride of calcium, c a piece 
of India-rubber tubing, m r p a Liebig's potassa bulbs. 

The Liebig's bulbs is partly filled with a solution of 
caustic potassa of a specific gravity 1.25 and weighed. 
Its peculiar form has been contrived in order to subject 
a gas passing through it completely to the action of the 
potassa, so as to be certain that all carbonic acid is ab- 
sorbed. 

The part of the combustion-tube nearest to the chlo- 
ride-of-calcium tube is first heated by fragments of ig- 
nited charcoal. These are obtained from a small sub- 
sidiary furnace. The heat is prevented from affecting 
the remainder of the tube by the movable screen g, 
which has gradually to be shifted an inch at a time 
down the length of the combustion -tube, until the 
whole has been subjected to a red heat. The bubbles 
of gas should not be made to pass through the caustic 
potassa faster than two in a second. At the end of the 
operation the charcoal should be fanned to raise the 
temperature to such a point that all the sugar may be 
with certainty burned. 

The point of the beak is then broken off, and a small 
quantity of air drawn through by affixing a cork to the 
tubep and applying the mouth. This removes the re- 
maining products of combustion. It is only necessary, 
in order to finish the analysis, to weigh again the chlo- 
ride-of-calcium tube and Liebig's bulbs, and to calculate 
the results. The increase of weight in the chloride of 
calcium indicates how much water it has gained, and 
from that the amount of hydrogen is easily found; the 

Describe Fig. 295. What is the Liebig's bulbs for, and why is it 
so shaped? "Describe the operation of combustion. What are the 
last steps of the analysis ? 



388 



DETERMINATION OF NITROGEN. 



increase in the potassa represents carbonic acid, pro- 
duced from the oxidation of the carbon. 

Where the substance analyzed is not as combustible 
as sugar, it is necessary to add chlorate of potassa to 
the oxide of copper, or else to use chromate of lead. 
The latter salt, not being hygrometric, may also be used 
for substances that would be decomposed by the warm 
oxide of copper when ground in a mortar. After it has 
been heated, it may be allowed to become perfectly cool 
before being put into the combustion-tube. 

Volatile fluids are weighed out in bulbs shaped as in 
Fig. 296, the bulbs being filled 
by the acid of a spirit-lamp 
and- the neck then sealed. 
After weighing, but before 
being put with the oxide of 
copper in the combustion- 



Fiq. 296. 




tube, the neck is broken off. 

The nitrogen in organic compounds may be determ- 
ined either as free gas or as ammonia. In the former 
case, the apparatus Fig. 297 is used. The eombustion- 



Fia. 207 




tube is two feet long, closed at one end like a test-tube. 
At the closed end, n, dry bicarbonate of soda is placed 
for six inches, then an inch and a half of oxide of cop- 
per. These are followed by a weighed quantity of the 
dried organic substance that has been ground with warm 
oxide of copper, a little pure oxide, and, finally, a layer 
of copper turnings five inches long. 

The copper turnings are for the purpose of setting 
free any nitrogen that may have united with oxygen to 

When the substance is not combustible, what must be done ? 
How are volatile fluids treated ? How may nitrogen be determ- 
ined ? Describe the determination as free gas. What are the cop- 
per turnings for ? 



DETERMINATION OP NITROGEN. 389 

form nitrous acid. The heating is conducted as in the 
former case, except that a part of the bicarbonate of 
soda must first be decomposed to drift out the air in 
the apparatus, and that the copper turnings must be 
kept at a red heat while the actual combustion is in 
progress. Instead of the analysis being terminated by 
drawing air through the apparatus, the remaining part 
of the bicarbonate is decomposed, so that the residue 
of nitrogen may be expelled by carbonic acid. 

The nitrogen is collected by the aid of the tube a, 
Fig. 297, in a graduated cylinder over mercury, the cyl- 
inder containing enough solution of caustic p6tassa to 
absorb the carbonic acid that comes over. 

In determining nitrogen as ammonia by the method 
of Varrentrapp and Will, the nitrogen is converted into 
ammonia by igniting the compound containing it with 
soda-lime, a mixture of caustic soda, 1, and caustic lime 
2 parts. The soda-lime furnishes hydrogen from its 
water to the nitrogen, forming ammonia ; the oxygen 
of the water unites with the carbon of the organic body. 
The ammonia is passed through a Varrentrapp and 
Will's bulbs, partly filled with hydrochloric acid of a 
specific gravity of 1.13, a, Fig. 298. The tube d serves 




to connect it with the combustion-tube a in the furnace 
g. By treating the contents of the bulb apparatus with 
bichloride of platinum the double chloride of platinum 
and ammonia is formed, and may be, after evaporation 
to dryness and washing with ether and alcohol, collect- 
ed on a filter and weighed. 

Sulphur compounds are oxidized as stated in the be- 
ginning of this lecture, and weighed as % sulphate of 

How is the nitrogen collected ? How may the nitrogen be con- 
verted into ammonia ? Describe the determination of nitrogen as 
free ammonia. How are sulphur and chlorine determined ? 



390 DIALYSIS. 

baryta. Chlorine is determined as chloride of silver, 
the substance being ignited with soda-lime, the mass 
dissolved in dilute nitric acid, and precipitated with ni- 
trate of silver. 

A process of analysis has been invented by Graham 
called Dialysis, in which the principles of liquid diffu- 
sion ar& brought into use. He divides all substances 
into two classes, crystalloids and colloids; the former 
being capable of crystallization, and possessing a tend- 
ency to diffusion through porous septa ; the latter being 
of a viscid, glutinous nature, like solutions of gum. The 
following table shows the time of diffusion, hydrochloric 
acid, the most diffusible of known bodies, being taken 
as unity. 

Table of Times of Equal Diffusion. 



Hydrochloric Acid 1 

Chloride of Sodium 2. 33 

Cane Sugar 7 



Sulphate of Magnesia .... 7 

Albumen 49 

Caramel 98 



The process of dialysis is best understood from an in- 
stance. Make a shallow tray by stretching a piece of 
parchment paper — that is, paper modified by sulphuric 
acid — over a hoop of gutta perch a. Having placed the 
mixture to be analyzed in the tray, float it in a dish of 
water. In a day or two the crystalloids will have dif- 
fused through the paper into the water, from which 
they may be obtained by evaporation. Arsenious acid 
may in this manner be separated from the contents and 
tissues of a stomach. 

Some colloids are found among inorganic bodies, as 
in the case of gelatinous silicic acid; but they are most- 
ly organic, and of complex atomic constitution. The 
crystalloid is the stable, w T hile the colloid is the change- 
able condition of matter. The latter is perpetually tend- 
ing to turn into the former. 

What is dialysis ? What classes are substances divided into, and 
what are the properties of each ? Give the rate of diffusion of some 
bodies. Describe the process of dialysis. What is the difference 
between the crvsfcilloid and colloid states of matter ? 



THE STARCH GROUP. 391 



LECTURE LXX. 

The Non-nitrogenized Bodies. — The Starch Group. 
— Starch. — Properties. — Tests for various Forms of 
Starch. — Production of Dextrine. — Action of Dias- 
tase. — British Gum. — Cane Sugar. — Action of Sug- 
ar on Polarized Light. — Grape Sugar. — Milk Sug- 
ar. — Gum. — Lignine. 

The non-nitrogenized bodies which we shall first 
consider are characterized by the peculiarity that they 
form a group, each member containing twelve atoms of 
carbon united with hydrogen and oxygen in the pro- 
portions to form water. They are, for the most part, in- 
different bodies. 

The Starch Group. 

Starch ^12^10^10 

Cane Sugar (crystallized) O^H^O^ 

Grape Sugar O l2 H l4: O l4: 

Fruit Sugar O l2 H 12 O l2 

Milk Sugar C l2 H ]2 12 

Gum C l2 H yi O n 

Lignine \C 12 H Q O a 

Etc. "Etc. 

Starch, Feculci, Amylum (C 12 IZ" 1O 1O ), is found abun- 
dantly in the vegetable kingdom, and may be obtained 
from potatoes by rasping, and washing the mass upon a 
sieve, the starch being carried off by the water. It may 
also be obtained from flour by making the flour into 
a paste with water and then washing it. The starch 
separates, and gluten is left behind. 

It is a white substance, commonly met with in irreg- 
ular prismatic masses, which shape it assumes while 
drying. It is almost insoluble in cold water, and en- 
tirely so in alcohol and ether. It consists of granules 
of different sizes, as in Fig. 299, those of the potato be- 
ing about the two hundred and fiftieth of an inch in di- 
ameter. 

What is the peculiarity of the starch group? Name the members 
of the starch group, and give their composition. Whence is starch 
obtained ? What are its properties ? 




392 STARCH. 

Fig. 299. When starch is heated in wa- 

ter, the covering membrane of 
each granule bursts open, and 
the interior matter dissolves out. 
If the proportion of starch be 
considerable, the whole forms a 
jelly-like mass, which may be 
dried into a yellowish body hav- 
ing the same constitution as 
starch itself. Gelatinous starch 
passes under the name of Amidine. 

With free iodine starch strikes a deep blue color. 
When water containing this compound is heated to 
212° the color totally disappears, and is not restored 
on cooling ; but if the source of heat be removed as 
soon as the color disappears, and when the temperature 
is not much above 160°, the color returns. Starch and 
iodine constitute an exceedingly delicate test for each 
other. Paper impregnated w^ith starch and iodide of 
potassium is blued by chlorine and bromine, and is use- 
ful as a test for ozone. 

In commerce, starch is found under various modifica- 
tions, such as Arrow-root, Tapioca, Cassava, Sago, 
Wheat starch, Potato starch, Mice starch, Tons les Mois, 
etc. It forms an important constituent of respiratory 
or heat-making food, and is said to exist in the ventri- 
cles of the brain. Innline, which is derived from the 
dahlia and other plants, is a substance approaching 
starch in many respects. 

When starch is boiled in water with a small quantity 
of sulphuric, hydrochloric, or nitric acid, it changes into 
Dextrine, a substance of the same composition ; the sul- 
phuric acid can be subsequently removed by carbonate 
of lime and filtration, dextrine being procured on evap- 
oration as a gummy mass. But if the ebullition be con- 
tinued for a longer time, the dextrine disappears and 
grape sugar comes in its stead. Starch may also be 
converted into grape sugar by the action of a peculiar 
ferment, Diastase, contained in an infusion of malt. 

What effect has hot water on it? What is amidine? What are 
the reactions of starch with iodine ? What are the commercial 
forms of starch? How is dextrine produced? How may grape 
sugar arise ? What are the properties of diastase ? 



CANE SUGAR. 393 

Gelatinous starch may in the course of a few minutes, 
at 160°, be converted into dextrine by this substance, 
and soon after into sugar. In either of these cases the 
presence of atmospheric air is not required, the final ac- 
tion being that the starch simply assumes four atoms 
of water, and becomes converted into grape sugar. 

When baked at a temperature of about 400°, starch 
becomes soluble in water, and passes in commerce un- 
der the name of British Gum, or Leiocome. 

Starch is used for stiffening various fabrics, and for 
making thin calicoes appear of greater substance than 
they really are. It is also largely employed in confec- 
tionery, cheap sugar-plums being composed of refuse 
starch, chalk, gypsum, etc. 

Cane Sugar, Sucrose {C l2 H d 9 +2HO), is found in 
the juices of many plants, as the sugar-cane, beet-root, 
sweet maple, Indian corn, and date-tree. It is chiefly 
extracted from the sugar-cane, which, after being crush- 
ed between rollers, yields a juice that is mixed with 
lime and boiled. A coagulum having been removed 
from it, it is rapidly evaporated at as low a temperature 
as possible, and then crystallized. In this state, after 
a brownish sirup, molasses, has drained from it, it pass- 
es in commerce under the name of Muscovado, or brown 
sugar. This is purified by boiling in water with albu- 
men, which, coagulating, separates many of the impuri- 
ties. The solution is then decolorized by animal char- 
coal, evaporated in a vacuum-pan at a temperature of 
150°, solidified in conical vessels, and, being washed 
with a Tattle clean sirup, is thrown into commerce as 
loaf sugar. Maple sugar is manufactured to a large 
extent in the United States, and beet-root sugar in 
France. 

From a strong solution sugar crystallizes in rhombic 
prisms, which are colorless ; they pass under the name 
of Sugar Candy. It is soluble in one third its weight 
of cold water. It has a sweet and proverbially charac- 
teristic taste. When heated it melts, and gives rise to 
a yellowish, transparent body called Barley Sugar ; but 
if kept at a temperature of 400°, it turns of a reddish- 
Why is air unnecessary? How is British gum formed? What 
are the uses of starch ? What are the sources of cane sugar ? How 
is it manufactured? What is sugar candy ? What is barley sugar? 

R2 



394 



ITS EFFECT ON POLAEIZED LIGHT. 



brown color, constituting Caramel. Sugar unites with 
various bodies, such as lime and oxide of lead, and with 
common salt yields a crystallized product. By casein 
it is transformed into lactic acid. 

A solution of sugar candy produces circular polariza- 
tion in a beam of light transmitted through it. This 
property, which is also exhibited by quartz, oil of lem- 
on, oil of turpentine, and some other substances, has 
been made use of to determine the purity of sirups. 
Crystallizable cane sugar, for example, produces a right- 
hand rotation; molasses, or uncrystallizable sirup, a 
left-hand rotation. The apparatus necessary for these 
operations is seen in Fig. 300. A glass tube, o o, full 



Fig. 3Q0. 




^JPfc^ 



of the solution, and closed at the ends by plates of glass, 
is placed in a metallic case, r s. A beam of red light is 
polarized by reflection from the mirror a b. At n is a 
Nicol's prism- capable of rotation around the line d i ; 
its angular movement is measured by a graduated cir-. 
cle, jp q, and vernier, m. The eye-piece, n^ being so ad- 
justed that the polarized beam is no longer visible, the 
tube full of solution, o o, is placed on the supports A B. 
A certain amount of light then passes, and the eye-piece 
must be rotated to the right or left, as the case may be, 

What is caramel? What effect has sirup on light? Describe 
the apparatus Fig. 300. Of what use is this property ? 



GRAPE SUGAR. 395 

to cut it off. The amount of rotation necessary ex- 
presses the rotatory power of the liquid. 

Grape Sugar — Glucose — Starch Sugar — Diabetic 
Sugar (C }2 lt u O u ) — is the substance just described as 
arising from the transmutation of starch under the in- 
fluence of acids, a process largely carried on in France 
as a commercial manufacture. It occurs naturally in 
many vegetable juices and in honey. 

Compared with cane sugar, it is much less soluble in 
water and less disposed to crystallize. It requires Im- 
parts of water for solution. It may be distinguished by 
its action with caustic alkalies and sulphuric acid, the 
former turning it brown and the latter dissolving it 
without blackening, while cane sugar is little acted on 
in the former instance and blackened in the latter. The 
two varieties may also be distinguished by being mixed 
with a solution of sulphate of copper, to which, if a so- 
lution of caustic potassa be added, blue liquids are ob- 
tained, and these being heated, the grape sugar throws 
down a green precipitate, which turns deep red, the so- 
lution being left colorless. The cane sugar alters very 
slowly, a red precipitate gradually forming and the liquid 
remaining blue. Grape sugar, like cane sugar, gives with 
common salt a crystallized compound. When heated to 
212° it loses two atoms of water and becomes C l2 H 12 ^12- 
At 284° it passes into caramel, C 12 S d O^ and at a high- 
er temperature is decomposed. 

Grape sugar and milk sugar possess the interesting- 
property of causing the reduction of silver, as a metallic 
film, from ammoniacal solutions of the nitrate of that 
metal. 

Milk Sugar — Lactine (O n II 12 12 ) — maybe obtained 
by evaporating whey to a sirup, and the crystals which 
then form are to be purified by animal charcoal. It is 
sparingly soluble, requiring five or six times its weight 
of water. The crystals are gritty between the teeth. 
It is through the alcoholic fermentation of this body 
that the Tartars produce intoxicating milk — koumiss. 

What are the sources of grape sugar? What are its properties 
compared with cane sugar? Describe the respective reactions with 
sulphate of copper and caustic potassa. What substances can re- 
duce silver on glass? How is milk sugar prepared? What are its 
properties ? — * 



396 GUM. — LiGNINE. 

Besides the foregoing, there are several subordinate 
varieties of sugar, among which may be cited 

Ergot Sugar C l2 H 13 O l3 , 

Eucalyptus Sugar C V2 H 14: 1 ^ 

and others, as honey, liquorice sugar, and mushroom 
sugar, or mannite. 

Gum. — Gum Arabic is obtained from several species 
of the mimosa or acacia, from the bark of which it ex- 
udes. It is in white or yellowish tears of a vitreous 
aspect. It dissolves in cold w T ater, forming mucilage, 
from which it may be precipitated pure as Arabine 
(0 12 H u ll ) by alcohol. Arabine produces arabinates 
with several metallic oxides, as those of lead and iron. 

Bassorine is the principle of Gum Tragacanth. It 
does not dissolve in water, but merely forms a jelly-like 
mass. With this substance should be classed Pectine 
((7 61 i^ 8 64 ), the jelly obtained from currants and other 
fruits. It furnishes Pectic Acid ( C 32 IT 20 28 , 2HO) by 
the action of bases. 

Gelose is the gelatinizing principle of Algae, Fuci, 
and Lichens. It is known as Japan Isinglass, and dif- 
fers from animal gelatin or isinglass in not putrefying 
nor precipitating with tannin. It contains no nitrogen, 
being {C 24i H 2l 2 ^. The birds' nests used in China for 
soup are constructed by a species of swallow from this 
substance. 

Lignine. — This substance, with Cellulose and other 
bodies, forms the woody fibre or ligneous tissue of 
plants. It occurs in a state of purity in the fibres of 
fine linen and cotton, and is, as is well known, of per- 
fect whiteness, insoluble in water and alcohol, and taste- 
less. Its specific gravity is about 1.5, and its durability 
turns on the association of resins, tannin, etc. Those 
kinds of wood which would otherwise decay rapidly 
from the absence of such preservatives, may be kept by 
artificially introducing into their pores solutions of cor- 
rosive sublimate, arsenic, chloride of zinc, tar, etc. 

Strong and cold sulphuric acid converts lignine into 

What other varieties of sugar are there ? Whence is gum arabic 
procured ? What are its properties ? What is the source of basso- 
rine and pectine? What is gelose? Where is lignine found ? 
How may wood be preserved ? What is the action of sulphuric acid 
on lignine? 



MODIFICATIONS OF SUGAK. 397 

dextrine, as may be shown by adding to that liquid 
pieces of linen, taking care that the temperature does 
not rise so as to blacken the mixture, which is to be 
well stirred and suffered to stand for a time. On dis- 
solving it then in water, and neutralizing by the addi- 
tion of chalk, dextrine is obtained ; or if, before neutral- 
izing, the solution be well boiled, grape sugar is pro- 
duced. 

Parchment paper, a valuable substitute for parch- 
ment, is made by steeping unsized paper in a mixture 
of equal parts of sulphuric acid and water at a temper- 
ature of 60°. 



LECTURE LXXI. 

Action of Agents on the Starch Group. — Action 
of Sulphuric Acid on Sugar.— Action of Lime on 
Sugar. — Production of Oxalic Acid. — Properties of 
Oxalic Acid. — Its Constitution; — Its Salts. — Sac- 
charic Acid. — Mucic Acid. — Pyroxyline^ its Prepa- 
ration and Properties. 

In the preceding Lecture we have explained the 
change of starch into sugar, and of lignine into dex- 
trine, under the influence of sulphuric acid. In the veg- 
etable world there can be no doubt that these and oth- 
er similar modifications arise from the action of many 
causes. On inspecting the constitution of this group, 
it will be seen that in theory this is to be done by the 
addition or abstraction of water. 

When melted grape sugar is mixed with strong sul- 
phuric acid, and the diluted solution neutralized with 
carbonate of baryta^ the sulphosaccharate of baryta is 
found in the solution. Sulpho saccharic Acid is a sweet- 
ish liquid, readily decomposing into sugar and sulphuric 
acid. 

When, in the process of converting cane sugar into 
grape sugar by boiling with sulphuric acid, the action 
is long continued, a dark-colored substance is formed, 
consisting of two different bodies, Uhnine and Zflmic 

How is parchment paper made ? How are changes in the starch 
group theoretically effected ? How is sulphosaccharic acid made ? 



398 OXALIC ACID. 

Acid, or, as they are termed by Liebig, Sacchulmine 
and Sacchidmic Acid. The latter is converted into the 
former by continued boiling in water. 

When a solution of grape sugar containing lime is 
kept for some time, the alkaline reaction of the lime 
finally disappears through the formation of Glucic Acid, 
the constitution of which is {C n H 5 5 -\-3HO). Un- 
der the influence of heat it becomes Apoglucic Acid 
( C lQ IT 9 Oq+2HO). Glucic acid is soluble, deliquescent, 
of a sour taste, and yields, for the most part, soluble 
salts. If grape sugar be boiled with potassa w T ater, it 
becomes dark from tha formation of glucic acid : this 
is Moore's Test for grape sugar. A dark substance is 
precipitated by an acid from this solution — JSlelasinic 
Acid (C 12 H 6 5 ). 

These are some of the less important results of the 
action of acid and alkaline bodies an the starch group ; 
there are others of far more interest. 

Oxalic Acid ( C 2 3 , HO+2Ag). — Oxaljc acid, found 
in many plants, as sorrel (Oxalis acetosella), is formed 
artificially by the action of nitric acid on starch or sug- 
ar, or any other of the starch group except gum and 
sugar of milk. One part of sugar is to be mixed with 
four of nitric acid and two of water; carbonic oxide and 
carbonic acid are evolved. The nitric acid is to be dis- 
tilled off until the residue will deposit crystals on cool- 
ing. These, being collected, are to be purified by redis- 
solving and crystallizing. Oxalic acid may be also man- 
ufactured very economically from sawdust, by mixing it 
with hydrate of potassa and soda in solution. The mix- 
ture becomes soluble in water, and must then be raised 
to 400° for some hours. Subsequently the heat is in- 
creased, but not to the point of destructive distillation. 
The result is a mixture of the oxalates of potassa and 
soda. Two pounds of sawdust yield one of oxalic acid. 
Tlyis prepared, it is consumed by the ton for calico 
printing, dyeing, and bleaching. 

The crystals of oxalic acid are oblique rhombic prisms, 
more soluble in hot than cold water, of an intensely acid 

When do sacchulmine and sacchulmic acid arise ? How are glu- 
cic and apoglucic acids made? How is oxalic acid artificially form- 
ed? Describe the production of oxalic acid from sawdust. What 
are the properties of crystallized oxalic acid ? 



DECOMPOSITION OF OXALIC ACID. 399 

taste, and poisonous to animals, death being produced in 
a few minutes. Chalk or magnesia is the antidote. The 
crystals contain one equivalent of saline water and two 
of water of crystallization. The latter may be removed 
by exposure to a low heat, the crystals then becoming a 
white powder and subliming without difficulty. Any 
attempt to remove the saline water and isolate the ox- 
alic acid (as C 2 3 ) leads to its decomposition. Thus, 
when the acid is heated with oil of vitriol total decom- 
position results ; equal volumes of carbonic oxide and 
carbonic acid are set free, for the constitution of oxalic 
acid is such that we may regard it as composed of an 
atom of each of these bodies. 

C 2 3 =C0 2 +CO. 
Upon this fact is founded one of the methods of pre- 
paring carbonic oxide. The gas- Fig. 301. 
eous mixture which results from 
the action of the oil of vitriol in the 
flask a, Fig. 301, is passed through 
a bottle, b, containing potassa wa- 
ter, which absorbs the carbonic acid, 
and the carbonic oxide may be col- 
lected at the water-trough. 

The production of oxalic acid from sugar by nitric 
acid is clue to the replacement of hydrogen by an equiv- 
alent quantity of oxygen. 

C l2 H 9 9 + 18 = C 12 O^q+JIq O q ; 
that is, one atom of dry sugar, with eighteen of oxygen, 
yield six of oxalic acid and nine of water. 

Salts of Oxalic Acid. 
There are three potassa salts: 1st. Neutral Oxalate 
of Potassa, made by neutralizing oxalic acid with car- 
bonate of potassa, crystallizes in rhombic prisms, soluble 
in three times their weight of water. 2d. Binoxalate of 
Potassa, made by dividing a solution of oxalic acid into 
two parts, neutralizing one with carbonate of potassa 
and then adding the other. It crystallizes in rhombic 
prisms, has a sour taste, dissolves in forty parts of wa- 
ter, and is found naturally in many plants, as sorrel and 

What change takes place when the water of crystallization is driv- 
en off? Describe the production of carbonic oxide. Name the po- 
tassa salts of oxalic acid. How arc thev made ? 




400 SALTS OF OXALIC ACID. 

rhubarb. 3d. Quadroxcilate of Potassa, made by divid- 
ing a solution of oxalic acid into four parts, neutralizing 
one and adding the rest. It crystallizes in octahedra, 
and is less soluble than either of the foregoing. These 
salts are sometimes used for the removal of ink stains 
from linen. 

Oxalate of Ammonia, prepared by neutralizing a hot 
solution of oxalic acid with carbonate of ammonia. It 
crystallizes in rhombic prisms which are efflorescent. 
Its solution is used, as has been already stated, as a test 
and precipitant of lime. When exposed to heat in a re- 
tort, it is for the most part decomposed into water, am- 
monia, carbonic acid, cyanogen, and other compounds ; 
but a flocculent substance called Oxamide also sublimes, 
the constitution of which is 

/7 2 (9 2 ,iV^=W 2 +2(CO), 
that is, containing the constituents of oae atom of amid- 
ogen and two of carbonic oxide. This remarkable sub- 
stance, when boiled with potassa, yields, through the de- 
composition of water, oxalate of potassa and ammonia. 
Oxamic Acid, C^H^OqN', is one of the results of the 
destructive distillation of binoxalate of ammonia at 450°. 
It is a yellowish powder, which, boiled in water, is re- 
converted into binoxalate of ammonia. 

Oxalate of Lime occurs naturally, forming the skele- 
ton of many lichens, and also as Paphides, crystalline 
bodies found in the cells of plants. Mulberry calculi 
are composed of it. It may be obtained by precipita- 
ting a lime-salt, as has just been said. It is soluble in 
nitric acid, and, ignited in a covered crucible, is con- 
verted into carbonate of lime, and finally into quick- 
lime. When dried, this salt stands at the head of sub- 
stances which become positive by friction. 

Saccharic Acid (C 12 IT 5 O u + 5HO), Oxalhydric 
Acid, is made by the action of dilute nitric acid in sug- 
ar. It is a pentabasic acid. 

Rhodizonic Acid ((7 7 7 + 3^TO) is obtained by the 
action of potassium on carbonic oxide at a red heat. 
When boiled it changes into Croconic Acid, a yellow 
body having the constitution C 5 0±+HO. 

Describe the properties of oxalate of ammonia. What is oxa- 
mide? What is oxamic acid? How does oxalate of lime occur? 
How are saccharic and rhodizonic acids made ? 



GUN-COTTON. 401 

Mucic Acid {C 12 HqO^+2HO), obtained by the ac- 
tion of dilute nitric acid on gum or sugar of milk, as in 
the preparation of oxalic acid by other members of the 
starch group. It requires sixty times its weight of wa- 
ter for solution. Decomposed by heat, it yields pyro- 
mucic acid. 

Xyloidine (CqII^O^ iV(9 5 ), made by the action of 
nitric acid, specific gravity 1.5 on starch, which is con- 
verted into a gelatinous body, and yields this substance 
as a white precipitate when acted on by water. Its or- 
igin is apparent from a comparison of its formula with 
that of starch. Xyloidine is insoluble in boiling water, 
but by the continued action of nitric acid changes into 
oxalic acid; 100 parts of starch yield 128 of xyloidine. 

Gtjn-Cotton — Pyroxyline. A remarkable compound, 
proposed in 1846 as a substitute for gunpowder by 
Schonbein. It may be prepared by the action of mono- 
hydrated nitric acid on cotton, paper, or sawdust, and 
still more conveniently by a mixture of nitric acid, spe- 
cific gravity 1.5, three parts, and sulphuric acid five 
parts, on those substances. 

It may also be made by soaking cotton for a few 
minutes in a mixture of pulverized nitrate of potassa 
and oil of vitriol, washing the result in hot water to free 
the cotton from the potassa salt, and finishing the wash- 
ing by a weak solution of ammonia ; 100 parts of cotton 
yield 170 of gun-cotton. Gun-cotton appears white 
like ordinary cotton, the fibre being little, changed ; it 
is harsh to the touch when dry, highly electric, and ex- 
plodes when heated to 400°, or when struck by a ham- 
mer. Its mechanical force much exceeds that of gun- 
powder, but the suddenness of its explosion has hith- 
erto rendered it difficult to replace powder by this 
substance. Baron Leuk, under the auspices of the Aus- 
trian government, has carried on a series of experiments 
for this purpose. 

A special variety of gun-cotton, possessing the ex- 
plosive property in a minor degree, but completely dis- 
solving in ether and alcohol, and forming a solution 
called Collodion, is extensively used as a photographic 

How is mucic acid made? How is xyloidine made, and what are 
its properties? How is pyroxiline made? Give another process. 
How does it compare with gunpowder? What is collodion ? 



402 PHOTOGRAPHIC PYROXYLINE. 

agent. Photographic pyroxyline requires many pre- 
cautions in its manufacture, and attention must be par- 
ticularly directed to the specific gravity of the acids, 
their relative quantities, the temperature of the mixture, 
and the time of immersion. Ten ounces, by measure, 
of sulphuric acid (1.84), and five ounces of nitric acid 
(1.37), with two ounces of water, are to be mixed. 
When the temperature has fallen to 130°, five drachms 
of cotton are to be added tuft by tuft, and kept in ten 
minutes. The cotton must, on removal from the vessel, 
be well pressed and washed. The qualities of the col- 
lodion as to tenacity, transparency, etc., depend princi- 
pally on the gun-cotton. For its use in photography, 
see Lecture XXIV. 

Pyroxyline is prone to spontaneous decomposition, 
with the evolution of nitrous acid. It is to be regard- 
ed as the nitrite of an organic base, having the form- 
ula (C 2i [-£T 16 (-^#4)4 2 o])' It is a substitution com- 
pound, in which four atoms of hydrogen of cellulose, 
C 2 ±II 2( >O 20l are replaced by four of nitrous acid. 



LECTURE LXXII. 

Metamorphoses of the Starch Group by Nitrogen- 
ized Ferments. — Action of Leaven. — Bread. — Fer- 
mentation of Sugar. — Yeast. — Making of Alcoholic 
Preparations. — Ferments. — Effect of Temjierature on 
Fermentation. — Nature of Ferments. — Making of 
Wine. — The Bouquet. 

In the preceding Lecture we have traced the action 
of the more powerful inorganic agents on the amyles, 
and seen how a variety of bodies of different characters 
arise, some of which, as oxalic acid, are of very consid- 
erable importance. 

But there is another system of changes which can be 
impressed on this group oi bodies far more curious in 
its nature, and leading to far more important results. 

When flour, made into a paste with water, is brought 

Describe the manufacture of photographic pyroxyline. What is 
the chemical nature of pyroxyline ? 



FERMENTATION.. 403 

in contact with leaven, that is to say, a similar dough, 
undergoing an incipient putrefactive fermentation, at a 
temperature of 60° or 10° bubbles of gas are disen- 
gaged, the paste swells up, and, when baked, forms 
leavened bread. This ancient process, which is now in 
use all over the world, depends on the action of the 
changing leaven being propagated to the sugar which 
the flour contains. The sugar is resolved into alcohol 
and carbonic acid, the former of which may be obtained 
by distilling the dough, and the bubbles of the latter, 
entrapped in the yielding mass, give to the bread the 
lightness for which it is prized. 

But the process may be better traced by observing 
the phenomena of alcoholic fermentation in the case of 
pure sugar. If we take a solution of sugar in water, it 
may be kept for a length of time without undergoing 
any change; but if nitrogenized matters, such as blood, 
albumen, leaven, etc., in a state of putrescent decay, be 
mixed with it at a temperature of 70°, the sugar rapidly 
disappears, carbonic acid is given off, and alcohol is 
found in the solution. The change is obvious. 

C 12 H 12 12 =2(0,H- 6 2 ) + 4(G0 2 )i 
that is, one atom ol dry sugar yields two ol alcohol and 
four of carbonic acid. The final action, therefore, of 
the ferment is to split the sugar atom into carbonic acid 
and alcohol. 

Of all ferments, Yeast, for these purposes, is the most 
powerful. It is a substance which arises during the 
fermentation of beer. The active part of yeast is com- 
posed of minute cells, which germinate to produce a mi- 
croscopic fungus, the Torula cerevisia?. It is probable 
that, in the various sugars, the first action is to bring 
them into the condition of grape sugar, and then the 
metamorphosis ensues. 

By an analogous transformation of the sugar contain- 
ed in fruits, different wines and intoxicating liquids are 
formed. Thus, if we take the expressed juice of grapes 
gpwhich has not been exposed to the contact of the air, it 
may be kept for a length of time without change; but 

What is leaven? What effect has it on dough? What is the. 
cause of the fermentation? Describe the alcoholic fermentation of 
sugar. Give the formulas. What is yeast? Describe the change 
in grape-juice. 



404 FEKMENTS. 

if a small quantity of oxygen be admitted to it, fermenta- 
tion at once sets in, the grape sugar diminishes, and al- 
cohol comes in its stead, carbonic acid being disengaged, 
and the nitrogenized ferment being deposited. If a so- 
lution of pure sugar be added, it is involved in the 
change, and portion after portion will disappear ; but, 
finally, the ferment itself is exhausted, and then any ex- 
cess of sugar remains unacted on. By the aid of ajar 
upon the mercurial trough these changes may be made 
manifest. 

It is obvious that the primary action is a change in 
the ferment, and the moment its particles are set in 
motion, the motion is propagated to the adjacent body, 
the particles of which submit in succession, and there- 
fore the fermentation is not a sudden action, but one 
requiring time. Moreover, it is plain that the action is 
limited ; a given quantity of ferment will transmute only 
a definite quantity of sugar. 

The ferments, or bodies which possess this singular 
quality, are nitrogenized bodies ; and inasmuch as non- 
nitrogenized bodies never spontaneously ferment while 
oxidizing, we impute the qualities in question to the ni- 
trogen. 

Temperature has a remarkable control over ferment 
action. The juice of carrots or beets, fermenting at 50°, 
will yield alcohol, carbonic acid, and yeast; but the 
same juices fermenting at 120° produce lactic acid, gum, 
and mannite. Under these circumstances, therefore, al- 
cohol is the product of fermentation at low, and lactic 
acid at high temperatures. 

But when milk ferments at 50° lactic acid is the chief 
product, while at 80° the casein acts like a yeast fer- 
ment, the milk sugar becoming transformed into grape 
sugar, and then resolving itself into alcohol and car- 
bonic acid. In this instance the action is the reverse 
of the former, lactic acid being the product of a low, and 
alcohol of a high temperature. 

A very remarkable decomposition takes place when^ 
casein ferment acts on sugar at 80° in presence of car- 
bonate of lime. Under these circumstances, carbonic 

What is the eventual result ? What is the action of the ferment ? 
What element do all ferments contain ? What effect has tempera- 
ture? What difference is there in its effect on beet-juice and milk? 



FERMENATION. 405 

acid gas and hydrogen are evolved, and Butyric Acid 
appears. On comparing the constitution of butyric acid 
with alcohol, it will be seen that the latter contains the 
elements of the former, with an excess of hydrogen, so 
that during this fermentation the alcohol atom is divided. 
In the acetous fermentation of alcohol the alcohol ab- 
sorbs four equivalents of oxygen, and is resolved into 
one of acetic acid and two of water, 

c 4 ir 6 o 2 + o 4 =c,n 4 o 4 +2iio. 

This change only takes place in the presence of decay- 
ing nitrogenized matter. 

All ferments possess certain properties in common, 
but each has its specific powers, and products which 
are evolved differ in different cases. Most commonly 
the activity of these bodies is excited by an incipient 
oxidation, the results of which would be to bring the 
ferment itself to a simpler constitution. In this respect, 
therefore, the first stage of fermentation is a combus- 
tion at common temperatures, or an eremacausis of the 
ferment itself; but this action is speedily propagated to 
the surrounding mass, which becomes involved in the 
change. Whatever, therefore, prevents the incipient 
oxidation of the ferment puts a stop to the whole pro- 
cess. By raising their temperature to 212°, and then 
cutting off the access of air, substances which would 
otherwise undergo a very rapid change may be kept 
for any length of time without alteration. On this prin- 
ciple, meats, milk, and other viands may be preserved, 
as is seen in the case of canned fruits, vegetables, etc. 

We have now pointed out the peculiarities of fer- 
mentation, showing that two successive stages may be 
traced in the process, the first arising in the oxidation 
of the ferment, by which its molecules are decomposed ; 
and the second, which consists in the propagation of 
this movement to the surrounding particles, upon which 
changes are impressed, the nature of which differs with 
the temperature and the specific action of the ferment 
itself. In fermentations the actual contact of the fer- 

Under what circumstances does butyric acid arise? Describe the 
change during the acetous fermentation. What is the nature of a 
ferment? What effect has high temperature on ferments? What 
stages are there in the action of ferments? Is contact of the fer- 
ment necessary ? 



406 WINE. 

ment itself is essential ; if it be separated by a dia- 
phragm of bibulous paper, the action is not propagated. 

Wine is made from the expressed juice of grapes, 
which, containing a nitrogenized body (albumen), when 
exposed to the air undergoes spontaneous fermentation ; 
the course of the action being, 1st, the oxidation of the 
vegetable albumen ; 2d, the propagation of its action to 
the grape sugar. If the sugar be in excess, the wine re- 
mains sweet ; if the albumen be in excess, the wine is 
dry. The wine, as soon as the first action is over, is re- 
moved into casks. The preservation of a certain amount 
of carbonic acid in solution gives rise to the effervescence 
seen in Champagne. During these changes, the bitar- 
trate of potassa, which exists naturally in grape-juice, 
and which, though sparingly soluble in water, is much 
less so in alcohol, is deposited. It goes under the name 
of Argol. Most other fruit -juices contain free acid, 
such as malic or citric, and hence good wine can not be 
made from them, because, if all the sugar be removed, 
they possess a sharp taste ; and if, as is commonly the 
case, a portion be left to correct the acidity, it is liable 
to run into a second fermentation. 

The bouquet of wine, a substance having the charac- 
ters of an essential oil, is partly natural to the grape 
and partly a result of fermentation. It has been repre- 
sented as a true ether, a combination of oxide of ethyle 
and oenanthic acid, C 18 -£T 18 3 . 

Inferior liquors, such as cider, perry, etc., are made 
from other vegetable juices, as those of apples and pears. 
Beer, porter, and ale are made from an infusion of malt, 
which is barley, a portion of the starch having been 
transmuted into sugar by partial germination. The 
principles of the fermentation are in all these cases the 
same. 

What is the ferment in the case of wine ? When is the wine 
sweet and when dry ? What is argol ? What is the bouquet ? What 
are beer, porter, and ale made from ? 



alcohol. 407 



LECTURE LXXIII. 

The Derivatives op Fermentative Processes. — Al- 
cohol. — Its Properties. — Its Existence in Wines. — 
lactic Acid. — Production and Properties. — Sulphur- 
ic Ether. — Preparation and Properties. — The Ethyle 
Group. — Chloride, Iodide, etc. — (Enanthic Ether. 

Alcohol {Hydrated Oxide of Ethyle), C 4 H 6 2 . 

By the distillation of wine or any other fermented 
saccharine juice, spirits of wine may be obtained. %\s 
first prepared, it contains a large quantity of water, 
which comes over with it. This product, being recti- 
fied, and the first portion preserved, yields a spirit con- 
taining twelve or fifteen per cent, of water. By put- 
ting this into a retort with half its weight of quick-lime, 
keeping the mixture a few days, and then distilling at a 
low temperature, absolute or anhydrous alcohol is ob- 
tained. 

Anhydrous alcohol is a colorless liquid, of a burning 
taste, and pleasant odor. Its specific gravity at 60° is 
0.794. It boils at 173°, and at a still lower point if 
slightly diluted with water, though the boiling point 
rises if the water be in greater proportion. It has not 
yet been frozen, though it thickens at —160°. The spe- 
cific gravity also varies with the amount of water pres- 
ent, and hence the purity of spirits of wine may be de- 
termined by ascertaining its density. Alcohol is very 
inflammable, and its vapor forms an explosive mixture 
with oxygen gas. It burns with a pale blue flame, with 
the production of carbonic acid and water, and is much 
used in chemical Investigations as furnishing a lamp- 
flame free from smoke, and as possessing an extensive 
range of solvent powers acting upon sulphur, resins, oils, 
and other bodies which are not acted on by water. 

Alcohol mixes with water in every proportion, heat 
being extricated at the moment of mixture, and the vol- 
ume of the combined liquids not equaling the sum of 

What is the chemical name for alcohol ? Plow is spirit of wine 
made? How is absolute alcohol produced? Describe the proper- 
ties of anhydrous alcohol. What are its uses ? 



408 SPIRIT OF WINE. 

the original quantities. Rectified Spirit has a specific 
gravity 0.825, containing 89 per cent, of absolute alco- 
hol. Proof Spirit, so named from the old gunpowder 
test, has a specific gravity 0.920, containing 49 per cent, 
of absolute alcohol. In that test the alcohol was mixed 
with gunpowder and fired. If the gunpowder took fire 
the spirit was over proof; if it did not, owing to excess 
of water in the spirit rendering it damp, it was under 
proof. Alcohol combines Avith many stiline bodies, be- 
ing apparently substituted for the water of crystalliza- 
tion. Such compounds are called Alcoholates. 

The strong wines, such as port and sherry, contain 
fi^m 19 to 25 per cent, of absolute alcohol, the light 
wines from 12 per cent, upward, beer, porter, etc.^from 
5 to 10 per cent. The amount of alcohol may be de- 
termined by carefully distilling a specimen of the wine, 
rendered alkaline, until one half its bulk has passed over, 
then filling the distilled portion up with water until the 
original bulk is reached, and ascertaining the specific 
gravity. By reference to a table the strength may be 
known. Or by decolorizing the wine and mixing it 
with%ry carbonate of potassa, the water may be ab- 
stracted, and the alcohol left floating on top of the aque- 
ous solution of carbonate. The specific gravity of the 
supernatant alcohol is 0.825 ; it therefore contains 89 
per cent, of absolute alcohol. Brandy, rum, gin, and 
whisky contain nearly half their weight of alcohol, and 
resemble proof spirit. 

The value of alcoholic liquids turns mainly on the 
flavoring principle, which is much modified by *age. 
Varieties in wine depend partly on the grape used and 
partly on the methods of manipulation. The flavor of 
gin is derived from juniper berries; that of whisky 
from the malt, particularly if it has been dried over 
peat ; that of rum from molasses ; Cura<joa from orange 
berries, etc. 

Many alcohols are enumerated — the Propylic, C 6 IT~ O y 
HO; the Butylic, C 8 IT 9 O, HO; the Caproic, C 12 H U 2 ; 

What is rectified spirit? Why is proof spirit so named? What 
are alcoholates ? What percentage of alcohol do port, sherry, etc. , 
contain ? How may the amount of alcohol be determined ? De- 
scribe the process with carbonate of potassa. What are the flavor- 
ing principles of gin, whisky, etc. 2 Name some of the alcohols. 



LACTIC ACID. 409 

the Caprylic, (7 4 J7" 18 2 , etc. The Amylic and Methylic 
alcohols will be hereafter described. 

Lactic Acid Fermentation. 

We have already seen that vegetable juices, as well 
as milkfjmll, under certain circumstances of tempera- 
ture, yield, during fermentation, lactic acid instead of 
alcohol. This acid may therefore be made by dissolv- 
ing a quantity of sugar of milk, putting it in a warm 
place, and allowing it to turn sour spontaneously. A 
part of the casein of the milk here acts as the ferment, 
and as lactic acid is set free, it coagulates the rest, and 
makes it insoluble. By the addition of carbonate of 
soda to neutralize the acid, this is prevented, and the 
ferment, retaining its activity, produces more lactic 
acid. When, by this process, all the sugar is exhaust- 
ed, the liquid is boiled, filtered, evaporated to dryness, 
and the lactate of soda dissolved out by hot alcohol. 
From this alcoholic solution the acid may be obtained 
by precipitating the soda by sulphuric acid. 

Lactic Acid (C 6 IT 5 5 +irO) is obtained as a sirupy 
solution by concentration in a vacuum over oil of vit-' 
^•iol. It is colorless, has a specific gravity of 1.215, is 
very sour, soluble in water and alcohol, dissolves phos- 
phates of lime, and coagulates albumen. It yields a 
complete series of salts, most of which are soluble. 
Among these salts, the most interesting are those of 
lime and zinc. 

Ether. — Sulphuric Ether. — Oxide of Ethyle, C& 
Lf 5 0. — Ether is prepared by distilling equal weights 
of alcohol and oil of vitriolj receiving the resulting va- 
por in a Liebig's condenser, a d h c, Fig. 302, the con- 
denser being cooled by water from the reservoir i flow- 
ing into the funnel c, the waste passing into the vessel 
6, and the ether distilling into the bottle e. The pro- 
cess is to be stopped as soon as the mixture begins to 
blacken. The first product may be rectified by redis- 
tillation from caustic potassa. 

Ether is a colorless and limpid liquid, of a peculiar 
odor and hot taste. It boils at 96°, and has not been 

How may lactic acid arise ? Why is carbonate of soda added ? 
What are the properties of lactic acid? How is ether made? De- 
scribe the apparatus. What are the proplfrtics of ether? 

S 



ETHER. 

Fig. 302. 




frozen ; its specific gravity at 60° is .V20. It volatilizes 
with rapidity, and therefore produces cold ; a drop of 
water covered by ether, upon which a current of air is 

^directed, may be frozen. It is combustible, and burns^ 
with the evolution of much more light than alcohol. 
The specific gravity of the vapor is 2.586. With oxy-. 
gen or atmospheric air it forms an explosive mixture, 
and, kept in contact with air, becomes acid from the 
production of acetic acid. It dissolves in alcohol in all 
proportions, but nine parts of water are required to dis- 
solve one of it; it also dissolves many fatty substances, 
and hence is of considerable use in organic chemistry. 

But its most important applications are, first, as a 
solvent for pyroxyline in the making of photographic 
collodion ; and, second, as an anaesthetic agent. The 
vapor of ether, when respired, produces at first an ex- 
hilarating effect, but a prolonged use eventually causes 

* a complete stupefaction, and permits the most painful 
operations to be performed without the knowledge of 
the patient. It can scarcely be regarded as dangerous 
to life if administered with care in the recumbent pos- 
ture and with an unembarrassed chest. The clothes 

In what fluids is ether soluble ? What are its most important ap- 
plications ? What precautions are necessary in its use as an anaes- 
thetic? • 



THE ETHYLE G110UP. 411 

should always be loosened, corsets removed, etc., and 
an examination of the heart and lungs made in the first 
instance. The anaesthetic powers seen in ether are also 
possessed by chloroform, the former being an Ameri- 
can, the latter a subsequent Scotch discovery. 

Ether is regarded as the oxide of a compound radi- 
cal, Ethyle, C±H 5 , a colorless gas, liquefying under a 
pressure of 2j atmospheres at 37°, and giving rise to a 
series of other bodies. 

The Ethyle Group. 

Ethyle, CJEt 5 =Ae 

Oxide of Ethyle =AeO 

Hydrated Oxide of Ethyle =^AeO+HO 

Chloride of Ethyle =AeCl 

Bromide " =AeB 

Nitrate " =AeO+N0 5 

Hyponitrite " =AeO+N0 3 

Etc. Etc. 

The oxide of ethyle, as has just been stated, is ether; 
the hydrated oxide, alcohol. 

Numerous ethers are produced by the action of a va- 
riety of acids upon alcohol ; they are called compound 
Ethers. 

Chloride of Ethyle {Hydrochloric Ether) may be 
made by saturating rectified spirits of wine with dry 
hydrochloric acid gas, and distilling the result at a low 
temperature, conducting the vapor through a bottle of 
warm water, and then condensing in a receiver sur- 
rounded by a freezing mixture. It is a colorless, vola- 
tile liquid, of a peculiar aromatic smell ; specific gravity 
.874. It boils at 60°, and at —10° crystallizes in cubes ; 
is soluble in 50 parts of water, and in all proportions in 
alcohol and ether. 

Iodide of Ethyle {Hydriodic Ether) is interesting as 
being the liquid from which ethyle w r as isolated by the 
action of zinc. It is obtained by the distillation of alco- 
hol, iodine, and phosphorus. 

Bromide, Sulphide, Cyanide, Sidphocyanide, and 
Fluoride of Ethyle are not of importance. Ilydrosul- 

What is the constitution of ether? Describe ethyle. Give the 
ethyle group. What are the compound ethers? How is chloride 
of ethyle made? What are its properties? Why is the iodide of 
ethyle interesting? What other ethyle compounds arc there? 



412 THE ETHYLE GROUP. 

plmric Ether, or Mercaptan { C^IT^+ITS), is procured 
by distilling hydrosulphate of sulphide of barium with 
sulphovinate of baryta. It is a colorless liquid, smelling 
like garlic; specific gravity .832 ; boils at 97°, and has a 
powerful affinity for mercury ; hence its name, mercu- 
riwn captans. 

Nitrate of Ethyle {Nitric Ether) may be made on a 
small scale by distilling equal weights of alcohol and ni- 
tric acid with a small quantity of nitrate of urea. The 
latter substance is used to prevent the nitric acid deox- 
idizing and giving rise to the production of nitrous 
ether. It is insoluble in water, has a density of 1.112, 
boils at 185°, and has a sweet taste. Its vapor explodes 
when heated. 

Hyponitrite of Ethyle {Nitrous Ether) may be made 
by passing the hyponitrous acid, disengaged from one 
part of starch and ten of nitric acid, through alcohol di- 
luted with half its weight of water and kept cold. It 
is a yellowish, aromatic liquid, having the odor of ap- 
ples; boils at 70°; specific gravity .947. The sweet 
spirits of nitre is a solution of this ether with aldehyde 
and other substances in alcohol. 

Carbonate of Ethyle — Carbonic Ether {AeO, Co 2 ), 
made by the action of potassium on oxalic ether, and 
distillation of the product with water. It floats on the 
surface of the distilled liquid, is an aromatic fluid, and 
boils at 259°. 

Oxalate of Ethyle {Oxalic Ether), prepared by dis- 
tilling four parts of binoxalate of potassa, five of sul- 
phuric acid, and four of alcohol into a warm receiver. 
The product is washed with water to separate any al- 
cohol or acid, and redistilled. It is an oily liquid, of an 
aromatic odor, boiling at 353°, and slightly heavier than 
water. With, an excess of ammonia it yields Oxamide 
and alcohol ; with a smaller proportion of ammonia it 
yields Oxamethane, C 6 IT 7 NOq. 

Many other ethers are formed by the union of oxide 
of ethyle with anhydrous acids, as perchloric, silicic, bo- 
racic, arsenic, cyanic, hydrocyanic, formic, acetic, benzo- 
ic, succinic, and citric. 

What is mercaptan ? How is the nitrate of ethyle made ? How 
is nitrous ether procured? How are the carbonate and oxalate 
made ? What other ethers are there ? 



FLAVORING PRINCIPLES. 413 

(Enanthic Ether (Ae 0, C 14 JET 13 2 ) is prepared from 
an oily liquid which passes over during the distillation 
of certain wines. It may be obtained by agitating the 
oil derived from brandy with carbonate of soda, which 
neutralizes the (Enanthic acid, and then distilling from 
chloride of calcium. It has a powerful vinous odor, is 
a colorless liquid, specific gravity .862 ; boils at 440° ; 
soluble in alcohol and ether, but not in water. It gives 
a peculiar aroma to the wines in which it is found. 
(Enanthic acid is prepared from it by the successive ac- 
tion of potassa and sulphuric acid. It is an oily body, 
becoming a soft solid at 55°. 

The compound ethers are found ready formed in 
many plants, and often give origin to their special odors 
and flavors; hence many of these can be imitated. 
Pine -apple Oil, for example, is butyric ether (C^JL^O, 
CqE^ 3 ), and may be made from butter or glycerine. 
Pear Oil is an alcoholic solution of the acetate of amyle, 
and Apple Oil is the valeriate of the same radical. 



LECTURE LXXIV. 

Derivative Bodies op Alcohol. — Sulphovinic and 
Phosphovinic Acids. — Products of Sulphovinic Acid 
at different Boiling Points. — The continuous Ether 
Process. — The continuous Olefiant Gas Process. — 
Dutch Liquid. — Successive Substitutions of Chlorine 
in it. — Heavy and Light Oil of Wine. — Sulphate of 
Carhyle and its derivative Acids. 

Sulphovinic Acid — Bisulphate of Ether (C^H 5 0, 
2S0 3 +2lI0). A mixture of sulphuric acid with an 
equal weight of alcohol is to be heated to the boiling- 
point, and then allowed to cool. It is diluted with wa- 
ter, and neutralized with carbonate of baryta, the sul- 
phate, of baryta subsiding. After filtering and evapo- 
rating, the solution is allowed to cool, and the sulpho- 
vinate of baryta crystallizes. From this the sulphovinic 
acid may be obtained by precipitating the baryta with 

How is cenanthic ether prepared, and what are its properties? 
Give the composition of pine-apple oil, etc. How is sulphovinic 
acid made? 



414 PHOSPHOVINIC ACID. 

dilute sulphuric acid, and evaporating the resulting so- 
lution in vacuo. It is a sirupy liquid, of a sour taste, 
giving rise to a series of soluble salts, which decompose 
at the boiling point, as will be presently seen. 

Phosphovinic Acid (C±H 5 0,P0 5 +2HO) is made 
on the same principles as the foregoing, phosphoric acid 
being substituted for sulphuric, and the resulting bary- 
ta salt being decomposed in the same way. It is a sir- 
ujfy liquid, of a sour taste, and dissolves in water, alco- 
hol, and ether readily. It is decomposed by heat. 

If sulphovinic acid be diluted so as to bring its boil- 
ing point below 260°, it is resolved at that temperature 
chiefly into sulphuric acid and alcohol. If the boiling 
point be from 260° to 310°, the distillation results chiefly 
in the production of hydrated sulphuric acid and ether. 
If, by the addition of sulphuric acid, the boiling point 
be carried above 320°, the action is more complex, but 
the chief product which passes over is defiant gas. 

The ordinary method of preparing ether is therefore 
very disadvantageous, because it is only within a par- 
ticular range of temperature that that body is evolved. 
At first the low temperature yields alcohol ; and, as the 
heat rises, the mixture begins to blacken, and olefiant 
gas to be evolved. 

To obviate these difficulties, a very beautiful proce&s, 
the continuous ether process, has been introduced. It 
consists in taking a mixture of eight parts by weight of 
sulphuric acid and five of alcohol specific gravity .834, 
the boiling point of which is about 300°. This is brought 
to that temperature in a flask by a spirit-lamp, as seen 
in Fig. 303 ; and alcohol of the same density is allowed 
slowly to flow into the flask from a bottle provided 
with a stopcock, the temperature being steadily kept at 
300°, and the mixture kept in a state of violent ebulli- 
tion. Water and ether distill over together, and may 
be passed through a Liebig's condenser; they collect 
in the receiver in separate strata ; or, if this does not 
take place at first, the addition of a little w r ater in the 
receiver insures it. 

How is phosphovinic acid made? What effects result from vari- 
ations in the boiling point of sulphovinic acid ? Why is the ordina- 
ry method of making ether disadvantageous ? Describe the contin- 
uous ether process. 



THE CONTINUOUS ETHER PROCESS. 4K 

Fig. 303. 




In this manner a very large quantity of alcohol may 
be converted into ether and water by the action of a 
limited amount of sulphuric acid ; and in a similar man- 
ner, by adjusting the boiling point so as to be between 
320° and 330°, defiant gas may be continuously ob- 
tained. All therefore that is required is to convey the 
alcoholic vapor through a mixture of oil of vitriol with 
half its weight of water which has the required boiling- 
point. In this process the acid does not blacken, and 
it is therefore much more advantageous than that de- 
scribed for the preparation of olefiant gas heretofore. 

Chloride of Olefiant Gas — Dutch Liquid ( C±H± Cl 2 ) 
— is prepared by mixing equal volumes of chlorine and 
olefiant gas in a large glass globe. It is a colorless and 
fragrant liquid, soluble in alcohol and ether, but less so 
in water. It boils at 180°, and when acted on by a so- 
lution of caustic potassa in alcohol it yields chloride of 
potassium, and a substance, CJJ^ CI, which, on being 
cooled by a freezing mixture, condenses into a liquid. 
This liquid, brought in contact with chlorine, absorbs 
that substance, and yields a compound, C±II 3 C7 3 , which 

What are the advantages of the continuous process? At what 
temperature does olefiant gas arise? How is Dutch liquid pre- 
pared ? What are its properties ? 



416 DUTCH LIQUID. 

may be decomposed by an alcoholic solution of potassa 
into chloride of potassium water and a new volatile 

There are an iodide and bromide of defiant gas which 
possess a constitution analogous to the chloride. 

When chlorine gas is made to act on Dutch liquid, 
four different substances may be successively formed 
by the gradual abstraction of hydrogen, and its equiva- 
lent substitution by chlorine. These substances are as 
follows : 

Dutch liquid CJI^Cl^ 

00 , C,H 3 Cl 3 

(2.) • C,E 2 Ch 

(3.) C,H Cl 5 

(40 Ct Cl & 

The first and second of these products are volatile 
liquids, the fourth is the perchloride of carbon, in which 
it appears that all .the four atoms of hydrogen in the 
Dutch liquid have been removed, and their places occu- 
pied by four atoms of chlorine. This perchloride of 
carbon is a white crystalline body, soluble in alcohol 
and ether ; its melting point is 320°. By passing its va- 
por through a red-hot porcelain tube it is decomposed, 
yielding (7 4 C7 4 and free chlorine, and this again gives 
rise to subchloride of carbon, C±Cl 2 , by being passed 
through a white-hot porcelain tube. The former of these 
bodies is a colorless liquid, the latter a silky solid. 

Heavy Oil of Wine (C^H 5 O y S0 3 ) may be procured 
by the destructive distillation of sulphovinate of lime, 
or by distilling 2 J parts of oil of vitriol and one of spirit 
of wine. It has a yellow color, a penetrating aromatic 
odor, and a specific gravity of 1.133. It can not be dis- 
tilled without decomposition; at 270° it is converted 
into alcohol, sulphurous acid, and olefiant gas. When 
boiled in water it yields sulphovinic acid, alcohol, and 
Light Oil of Wine, which, after standing a few days, 
deposits white inodorous crystals of Etherine, C 4 IT^ 
The residue, which still remains liquid, is Etherole, C 4 JI 4 . 
It is a yellow liquid, lighter than water, and soluble in 
alcohol and ether. 

Describe the action of chlorine on Dutch liquid. Describe the 
products that arise. How is heavy oil of wine procured? What 
changes occur on heating it ? 



THE ACETYLE SEKIES. 417 

Sulphate of Carbyle (C±H±, 4#0 3 ) arises when the 
vapor of anhydrous sulphuric acid is absorbed by pure 
alcohol. It is a white crystalline body. When dis- 
solved in alcohol and water added, the solution neutral- 
ized by carbonate of baryta, filtered, concentrated, and 
then mixed with alcohol, the Mhionate of Baryta pre- 
cipitates. This, when decomposed by dilute sulphuric 
acid, yields Hydrated Ethionic Acid (C±H 5 0, 4S0 3 + 
2JTO). Ethionic acid yields a series of salts, many of 
which can be obtained in crystals. On being boiled, a 
solution of ethionic acid yields sulphurous acid and Ise- 
thionic Acid, the peculiarity of which is that it is isomeric 
with sulphovinic acid, both containing C 4 H 5 0, 2S0 3 + 
HO. Methionic Acid arises from the action of hot sul- 
phuric acid on ether. Althionic Acid is made by act- 
ing on alcohol with great excess of sulphuric acid. The 
last two acids are by some regarded as compounds of 
sulphovinic with isethionic acid. 



LECTURE LXXV. 

Oxidation of Alcohol. — The Acetyle Series. — Alde- 
hyde. — Its Preparation and Properties. — Aldehydic 
Acid. — The Flameless Lamp. — Acetal produced by 
Platinum Black. — Acetic Acid, Production of. — Na- 
ture of the Change from Alcohol to Acetic Acid. — 
Salts of Acetic Acid. 

It has already been stated that when alcohol is burned 
in contact with oxygen gas or atmospheric air, the sole 
products of the combustion are carbonic acid and wa- 
ter ; but when the oxidation is partial, the hydrogen is 
removed by preference, and a new series of bodies is 
the result, designated as 

The Acetyle Series. 

Acetyle, <7 4 iT 3 =Ac 

Oxide of Acetyle =Ac 

Hydrated Oxide of Acetyle (Aldehyde) =AcO +HO 

Acetylous Acid (Aldehydic Acid) =Ac0 2 +HO 

Acetic Acid =Ac0 3 +HO 

Describe the sulphate of carbyle. How is ethionic acid produced ? 
How are isethionic, methionic, and althionic acids made? What is 
the difference between the partial and total oxidation of alcohol ? 
Give the acetyle series. 

S 2 



418 ALDEHYDE. 

Acetyle differs from ethyl e by containing only three 
atoms of hydrogen instead of five. 

Hydrated Oxide of Acetyle {Aldehyde) may be ob- 
tained by distilling a mixture of 4 parts of alcohol, 6 of 
oil of vitriol, 4 of water, and 6 of binoxide of manganese, 
into a receiver cooled by ice. The product is redistilled 
from chloride of calcium. It then consists of aldehyde, 
acetal, ether, and alcohol. It is next mixed with twice 
its volume of ether and saturated with dry ammonia. 
Two parts of the crystalline compound of aldehyde and 
ammonia, dissolved in two of water, with a mixture of 
three of oil of vitriol and four of water, are distilled, and 
the distillate redistilled from chloride of calcium at a 
temperature of 87°. It is a colorless liquid, of a suffo- 
cating odor ; specific gravity .790, boiling point 68°. It 
is soluble in water, alcohol, and ether. It slowly ox- 
idizes in the air, and more rapidly under the influence 
of the black powder of platinum, producing acetic acid. 
Heated with caustic potassa it yields aldehyde resin, a 
brown body of a resinous aspect. Aldehyde is so called 
because it contains the elements of alcohol minus two 
atoms of hydrogen {Alcohol Dehydrogenatus). 

When pure aldehyde is kept for a length of time at 
32° in a close vessel it yields Elaldehyde, a substance 
isomeric with itself, but possessing different properties, 
the specific gravity of its vapor, for example, being three 
times that of the vapor of aldehyde. From it there is 
also produced, at common temperatures, a second iso- 
meric body, Metaldehyde. 

Fig. 804 Aldehydic Acid may be obtained 

by digesting oxide of silver with, al- 
dehyde, and precipitating the metal 
with sulphureted hydrogen. It con- 
tains one atom of oxygen less than 
acetic acid, and is one of the prod- 
ucts of the slow combustion of ether 
in Davy's flameless lamp, which may 
be made by putting a small quantity 
of ether in a jar, Fig. 304, and sus- 
pending in the vapor, as it mixes with 
atmospheric air, a coil of platinum 

How is aldehyde made ? What are its properties ? What is the 
origin of its name ? What is elaldehyde ? How is aldehydic acid 
made ? What is Davy's flameless lamp? 




ACETAL. — ACETIC ACID. 



419 




wire which has been recently ignited. The wire remains 

incandescent as long as any FiQt 305# 

ether is present. The same 

result may be obtained by 

putting a spiral of platinum 

wire, Fig. 305, or a ball of 

spongy platinum over the 

wick of a spirit-lamp. The 

lamp being lighted for a 

short time and then blown 

out, the platinum continues 

incandescent, evolving a peculiarly acrid vapor. 

Acetal (C Q IT Q 3 )^ containing the elements of ether 
and aldehyde, is produced by the oxidation of the vapor 
of alcohol by black powder of platinum, the alcohol be- 
ing placed in a jar with moistened platinum black in a 
capsule above it. In the course of several days the al- 
cohol will be found to have become sour ; it is then to 
be neutralized with chalk and distilled. Chloride of 
calcium separates an oily liquid from the distilled prod- 
uct. This, on being distilled at a temperature of 200°, 
yields acetal. It is a colorless, aromatic, mobile liquid, 
specific gravity .825, and boiling at 203°. It produces, 
under the influence of an alcoholic solution of caustic 
potassa, by absorbing oxygen from the air, resin of al- 
dehyde. 

Acetic Acid — Pyroligneous Acid — Vinegar {C±H 3 
3 -\-HO). When dilute alcohol is dropped on plati- 
num black, oxidation takes place, and Fm soe. 
the vapors of acetic acid are formed. 
On the large scale it is also made by al- 
lowing a mixture of alcohol, water, and 
a small quantity of yeast, b,Fig. 306, to 
flow over wood shavings which have 
been steeped in vinegar, contained in a 
barrel, through which atmospheric air 
is allowed to circulate by the apertures 
ccc. The temperature rises and the 
acetification goes on with rapidity, the product being 
collected in the receiver a. Vinegar also is formed by 

Describe Fig. 305. Describe the preparation and properties of 
acetal. How is acetic acid made ? Describe Fig. 306. How docs 
vinegar arise ? 




420 ACETIC ACID. 

the spontaneous souring of wines or beer containing 
ferment, and kept in a cask to which atmospheric air 
has access. During the destructive distillation of dry 
wood, acetic acid, hence called pyroligneous acid, in an 
impure state is found among the products. 

Anhydrous acetic acid is obtained by distilling eight 
parts of dry acetate of potassa with three of oxychloride 
of phosphorus. It is a colorless liquid, specific gravi- 
ty 1.07, boiling point 280°, and dissolves in water, falling 
at first to the bottom like a heavy oil. 

Very strong acetic acid may be made by distilling 
powdered anhydrous acetate of soda with three times 
its weight of on. of vitriol. The product is then redis- 
tilled and exposed to a low temperature, when crystals 
of hydrated acetic acid form ; the fluid portion is poured 
off and the crystals suffered to melt. It is a colorless 
liquid, crystallizing below 60° in plates or tufts ; has a 
very pungent odor, and, placed 'on the skin, blisters it; 
it. boils at 243°, the vapor being inflammable. The spe- 
cific gravity of the liquefied crystallized acid is 1.0635, 
and the density increases on dilution until the acid con- 
tains one equivalent of anhydrous acid to three of water, 
when it is 1.073 ; on farther dilution the density dimin- 
ishes. It also dissolves in alcohol and ether. In an im- 
pure state as vinegar, its taste, odor, and applications are 
well known. Acetic acid is largely used in photograph- 
ic operations to retard the action of reducing agents 
upon nitrate of silver, constituting an important ingre- 
dient of developers, as they are called. 

If acetic acid be compared with alcohol, 

Alcohol CJIsOv 

Acetic Acid CJI^O^ 

it is seen to differ in the circumstance that two hydro- 
gen atoms have been removed from the alcohol and 
their places taken by two oxygen atoms ; hence the va- 
rious processes for its production are easily explained. 
Acetic acid gives rise to several important salts. 

Acetate of Potassa {KO, C±IT 3 3 ) is obtained by neu- 

How is anhydrous acetic acid made ? How may strong acetic 
acid be made? What are its properties? Of what use is acetic 
acid? What is the difference between acetic acid and alcohol? 
Name some of the salts of acetic acid, and give their methods of 
preparation. 



SALTS OF ACETIC ACID. 421 

tralizing acetic acid with carbonate of potassa, evapo- 
rating to dryness, and fusing. This salt is very deli- 
quescent, has an alkaline reaction, is soluble in its weight 
of water and twice its weight of alcohol. 

Acetate of Soda is made on the large scale by satu- 
rating the impure pyroligneous acid formed in the de- 
structive distillation of wood with lime, and then de- 
composing the acetate of lime with sulphate of soda. 
The sulphate of lime precipitates, the solution being 
crystallized, and the crystals subsequently purified by 
draining, fusion, solution, and recrystallization. The 
crystals effloresce in the air, and are soluble in water 
and alcohol. 

Acetate of Ammonia {Spirit of Mindererus). — The 
solution is made by saturating acetic acid with carbon- 
ate of ammonia, and the solid by distilling acetate of 
lime and chloride of ammonium. The acetate of ammo- 
nia passes over, and chloride of calcium is left. 

Acetate of Alumina is made by the decomposition of 
a solution of alum by acetate of lead. It is much used 
by dyers as a mordant. 

Acetates of Lead. — 1st. Neutral Acetate (Sugar of 
Lead) may be made by dissolving litharge in acetic 
acid. It occurs in colorless prismatic crystals, and 
also in crystalline masses. It has a sweetish, astringent 
taste, from which its commercial name is derived. It is 
soluble in less than two parts of water and in eight of 
alcohol. The crystals effloresce. 2d. Subacetate of 
Lead (Sesquibasic Acetate) is formed by partially de- 
composing the neutral acetate by heat. Its solution is 
known as Goulard^s Water. Two other subacetates 
may be made by the action of ammonia on the neutral 
salt. Their solutions have an alkaline reaction, absorb 
carbonic acid from the air, giving rise to a precipitate 
of the basic carbonate, and constituting a delicate test 
for that gas. 

Acetates of Copper. — 1st. Neutral Acetate (Crystal- 
lized Verdigris) , made by dissolving verdigris in hot 
acetic acid. On cooling, it yields green crystals, soluble 
in five parts of boiling water, and also in alcohol. It is 
used as a paint. 2d. Bibasic Acetate of Copper ( Ver- 

How many acetates of lead are there? Giye their properties. 
How is verdigris made? 



422 DERIVATIVES OF ACETYLE. 

digris) may be made by the aGtion of vinegar and air 
conjointly on metallic copper. Plates of copper are al- 
ternated with pieces of cloth steeped in acetic acid. As 
they become covered with verdigris, it is removed as a 
blue-green powder, and the operation continued until 
the copper is exhausted. Verdigris is a mixture of sev- 
eral acetates, one of which may be obtained by digest- 
ing it in warm water ; a second arises on boiling this ; 
the insoluble residue contains a third. 



LECTURE LXXVI. 

Derivatives of Acetyle. — The Kakodyle Group. — 
Chloracetic Acid. — Acetone. — Chloral. — Hydrochlo- 
ric Ether. — Action of Chlorine on the Ethers. — 
— Xanthic Acid. — The Kakodyle Group. — Oxide. 
— Chloride. — Kakodylic Acid. 

Chloracetic Acid (HO,C±U 2 3 Cl) is produced 
when chlorine is passed through a mixture of two parts 
of glacial acetic acid and one of water, the sunlight be- 
ing excluded. It is said to produce definite salts. 

When glacial acetic acid is exposed to sunshine in a 
jar of chlorine, white flocculi are formed ; they are tri- 
chloracetic acid (HO, C^C1 3 3 ). The hydrogen of the 
acetic acid is replaced by chlorine. Chlorocarbonic, 
carbonic, and oxalic acids are at the same time formed. 
The salts of this acid are soluble in water. 

Sidphacetic Acid arises when acetic acid is acted on 
by anhydrous sulphuric acid. Its composition is (C 4 
H 2 2 , 2S0 3 , 2HO). It forms deliquescent crystals and 
bibasic salts. 

Acetone — Pyroacetic Spirit (C 6 ir 6 2 ) — is obtained 
when acetate of lime is distilled with excess of quick- 
lime, or when two parts of acetate of lead and one of 
lime are heated in an iron retort. The distillate is re- 
distilled from a water-bath. It is a limpid, colorless, 
and volatile liquid, specific gravity .792, boiling at 

What is the composition of verdigris ? How is chloracetic acid 
produced ? What results on exposing acetic acid to chlorine ? How 
is sulphacetic acid formed ? What are the properties of pyroacetic 

spirit ? 



CHLORAL. 423 

132° ; burns with a bright flame, and is soluble in wa- 
ter, ether, and alcohol. By the action of chlorine, 
three substitution products are obtained, in which two, 
three, and four atoms of hydrogen are replaced by chlo- 
rine. Nordhausen oil of vitriol, distilled with acetone, 
yields an oily body, the constitution of Avhich is C 3 H 2 ; 
it is lighter than water, and has an odor of garlic. 

Sir R. Kane considers acetone to be the hydrated ox- 
ide of a radical, Mesityle, C 6 H^ and has produced the 
oxide and chloride of mesityle. Zeise also discovered 
a compound consisting of the oxide of mesityle and bi- 
chloride of platinum. 

Chloral ( CJELCl^ 6> 2 ). — When dry chlorine is passed 
into anhydrous alcohol, and the action finished by the 
aid of heat, hydrochloric acid is produced ; and on its 
ceasing to appear, if the product be agitated with three 
times its volume of oil of vitriol, and the mixture 
warmed, an oily liquid floats on the acid ; this is chlo- 
ral. It may be purified by successive distillation from 
oil of vitriol and quick-lime. It is an oily, colorless liq- 
uid, which causes a flow of tears, leaves a transient 
greasy stain on paper, has. a density of 1.502, boils at 
206°, is soluble in water and alcohol, and gives no pre- 
cipitate with nitrate of silver. When kept for a length 
of time in a sealed tube, it spontaneously becomes white, 
solid chloral. In this condition it is little soluble in 
water, and reverts to its other state by being warmed. 

If chlorine acts on alcohol containing water, heavy 
Hydrochloric Ether is formed. It is a colorless and 
volatile liquid. 

The action of chlorine upon common ether, and also 
upon the compound ethers, is very interesting. It con- 
sists in the gradual removal of hydrogen, chlorine being 
substituted for it. This, in many instances in which the 
aid of the sunlight is resorted to, terminates in the en- 
tire removal of the hydrogen. In the compound ethers 
it is the basic hydrogen which is removed, w T hile that 
of the acid escapes, as in the case of chlorureted acetic 
and chlorureted formic ethers. When the vapor of 
light hydrochloric ether is acted upon by chlorine gas, 

What is the chemical composition of acetone ? How is chloral 
made? What changes may occur in it? What is the action of 
chlorine on the ethers? 



424 KAKQDYLE. 

a complete series of compounds may be obtained, the 
hydrogen eventually disappearing : 

Hydrochloric Ether . CJI b Cl 

Monochlorureted Hydrochloric Ether C±H±Cl 2 

Bichlorureted " " CJS 3 Cl 3 

Trichlorureted " " C±H 2 C!± 

Quadrichlorureted " " CJI C/ 5 

Perchloride of Carbon ,(? 4 Cl 6 

furnishing, therefore, a very striking instance of the 
doctrine of substitution. 

Xanthic Acid (-(7 6 i2^# 4 O+HO). — Hydrate of potas- 
sa is to be dissolved in twelve parts of alcohol, specific 
gravity .8, and bisulphide of carbon dropped into the 
solution until it ceases to have an alkaline reaction. On 
cooling to zero, the xanthate of potassa crystallizes ; it 
is to be dried in vacuo. It is soluble in water and alco- 
hol, but not in ether, and from it xanthic acid may be 
procured by the action of dilute hydrochloric acid. 
Xanthic acid is an oily liquid, heavier than water, which 
first reddens and then bleaches litmus paper. At 15° 
it is decomposed into alcohol and bisulphide of carbon. 
It is also decomposed by the action of the air. 

Kakodyle (C^JIqAs—ICcT) is a compound radical 
which gives rise to an extensive .group of bodies, in 
which it acts the part of a metal. 

The Kdkodyle Group. 

Kakodyle, C A H % As =Kd 

Oxide of Kakodyle =KdO 

Chloride " =KdCl 

Iodide " =KdI 

Sulphide " =KdS 

Etc. Etc. 

Kakodyle may be obtained by decomposing the chlo- 
ride of kakodyle with metallic zinc in an apparatus 
filled with carbonic acid, and may be purified by redis- 
tillation from zinc, similar precautions being taken to 
exclude atmospheric air. It is a colorless liquid, of a 
highly^ofiensive odor, whence its name, taking fire spon- 
taneously in the air, oxygen, or chlorine, boils at 338°, 
crystallizes at 20° in square prisms, and is decomposed 

Give the compounds of hydrochloric ether. .How is xanthic acid 
produced ? What is kakodyle ? How is it obtained ? What are its 
properties ? 



COMPOUNDS OF KAKODYLE. 425 

at a red heat into defiant gas, light carbureted hydro- 
gen, and arsenic. It is very poisonous. 

Oxide of Kakodyle — ATkarsine — Cadet* s Fuming 
Liquor — is prepared by the distillation of acetate of po- 
tassa and arsenious acid, receiving the products in an 
ice-cold vessel, the temperature being finally carried to 
a red heat. The oxide comes over in an impure state, 
sinking to the bottom of the other products. It is to 
be decanted, washed with water, boiled, and then distil- 
led in a vessel full of hydrogen from hydrate of potassa. 
It is a colorless liquid, spec. gr. 1.64 ; boils at 300°, and 
solidifies at 9°; is insoluble in water, but dissolves in al- 
cohol and ether ; is excessively poisonous, possessing a 
smell like concentrated garlic. Heated in the air, it burns, 
producing carbonic acid, water, and arsenious acid. 

Chloride of Kakodyle may be procured by the action 
of a dilute solution of corrosive sublimate on a dilute al- 
coholic solution of oxide of kakodyle. A white precip- 
itate falls, which, distilled with strong hydrochloric acid, 
yields corrosive sublimate ; water and the chloride of 
kakodyle passes over. When purified by chloride of 
calcium and distilled in an atmosphere of carbonic acid, 
it is a colorless liquid, of a very offensive odor, heavier 
than water and insoluble therein, but soluble in alcohol. 
It is very poisonous. It boils at about 212°, the vapor 
taking fire in the air. 

Kakodylic Acid — Alcargen (Kd0 3 ) — may be made 
by the action of oxide of mercery upon oxide of kako- 
dyle under the surface of watSP at a low temperature. 
Kakodylic acid forms crystals which deliquesce in the 
air, are soluble in water and alcohol, but not in ether. 
It is not acted upon by oxidizing agents, such as nitric 
acid, but is reduced to oxide of kakodyle by several de- 
oxidizing bodies. It is not poisonous, though it con- 
tains 56 per cent, of arsenic: seven grains of it produced 
no effect on a rabbit. 

Kakodyle furnishes a complete series of bodies — the 
iodide, sulphide, cyanide, and a substance isomeric with 
the oxide, which has the name of parakakodylic oxide. 

How is the oxide of kakodyle made? What are its properties? 
How is the chloride formed? What are its properties? How is 
kakodylic acid made? How much arsenic does it contain? What 
properties have the kakodyle compounds in common ? 



426 THE WOOD-SPIRIT GEOUP. 

The preparation of these compounds is very dangerous, 
from their explosibility and poisonousness. The cyan- 
ide of kakodyle, diffused in the smallest quantity through 
the atmosphere, produces a sudden cessation of muscu- 
lar power in the hands and feet, giddiness, and insensi- 
bility. 



LECTURE LXXVIL 

The Wood -Spirit Group. — Methyle. — Its Oxide and 
Hydrated Oxide. — Salts of Methyle. — Formic Acid, 
Natural and Artificial Production of. — Chloroform. 
— Its Anaesthetic Properties. — Action of Chlorine on 
the Oxide of Methyle. — Substitutions in Chloride of 
Methyle. 

In the destructive distillation of wood in the prepa- 
ration of pyroligneous acid, there passes over about one 
per cent, of a body to which the name of wood-spirit 
has been given. This is the hydrated oxide or alcohol 
of a compound radical, Methyle. 

Methyle, C 2 H 3 =Me 

Oxide of Methyle =MeO 

Hydrated Oxide of Methyle =MeO+HO 

Chloride of Methyle =MeCl 

Etc. Etc. 

Methyle is a gas, specific gravity 1.036, produced by 
decomposing iodide of Jfethyle by zinc. 

Oxide of Methyle — Methylic Ether — Wood Ether 
(C 2 H 2 0). — This substance is made from the hydrated 
oxide, on the same principle that ether is made from al- 
cohol. One part of wood-spirit and four of oil of vit- 
riol being heated in a flask, the vapor is passed through 
a small quantity of caustic potassa solution and received 
at the mercurial trough. It is a permanently elastic 
gas, colorless, and has a specific gravity of 1.59; burns 
with a pale blue flame, is very soluble in water, which 
takes up thirty-three times its volume of it, and yields it 
unchanged when heated. 

When does wood-spirit arise ? What is the composition of me- 
thyle ? How is methyle produced ? How is the oxide of methyle 
made? 



COMPOUNDS OF METHYLE. 427 

Hydrated Oxide ofMethyle — Wood-Spirit — Pyroxy- 
lic Spirit — may be separated from crude wood vinegar 
by distillation. It passes over with the first portions 
along with a little a,cid, which, being neutralized with 
hydrate of lime, the wood-spirit may be separated from 
the oil which floats on its surface and redistilled. The 
product thus obtained may be rectified in the same 
manner as common alcohol, and rendered anhydrous by 
quick-lime. It is then a colorless liquid, of a hot taste 
and peculiar smell, like peppermint. It boils at 150°, 
and has a specific gravity of .7398 at 60° ; the density 
of its vapor is 1.125. It is soluble in water, alcohol, and 
ether in all proportions, and may be burned like spirit 
of wine, exhaling a peculiar odor. Its solvent powers 
resemble those of alcohol ; it may be used as a substi- 
tute for that fluid in the manufacture of fulminating sil- 
ver. It dissolves resins and oils. It is a powerful anti- 
septic. Methylated Spirit contains ten per cent, of me- 
thylic alcohol and 90 per cent, of alcohol. 

Chloride ofMethyle (MeCl) may be made from the 
reaction of sulphuric acid upon common salt and wood- 
spirit. It is a colorless gas, which may be collected 
over water, and has a density of 1.731. it has a pecul- 
iar odor, is inflammable, and may be decomposed by 
passing through a red-hot tube. Chloride of lime, act- 
ing upon pyroxylic spirit, gives rise to methylic chloro- 
form. 

Sulphate of Oxide of Methyle (MeO, S0 3 ) may be 
prepared by distilling one part of wood-spirit with eight 
or ten of oil of vitriol ; the product is to be washed 
with water and redistilled from caustic baryta. It is 
an oily, neutral liquid, smelling like garlic; specific 
gravity 1.324; boils at 370°. It is not soluble in wa- 
ter, but is decomposed by that liquid, especially at the 
boiling point, into sulphomethylic acid and hydrated 
oxide of methyle. It is to be observed that in the se- 
ries of wine alcohol there is no compound correspond- 
ing to this. 

Nitrate of Oxide ofMethyle (Me0>]¥0 5 ) is obtained 

How is pyroxylic spirit made and what are its properties ? What 
is methylated spirit ? What are the properties of chloride of me- 
thyle ? Describe the preparation and properties of sulphate of oxide 
of methyle. State the properties of nitrate of oxide of methyle. 



428 FORMIC ACID. 

by the action of a mixture of wood-spirit and oil of vit- 
riol upon nitrate of potassa. It is a colorless liquid, 
heavier than water; boils at 150° ; burns with a yellow 
flame ; its vapor explodes when h^ted. In a solution 
of caustic potassa, it decomposes into nitrate of potassa 
and wood-spirit. 

Oxalate of Oxide of Methyle (MeOC 2 3 ) is made by 
distilling oxalic acid, wood- spirit, and oil of vitriol. 
The liquid which is collected is allowed to evaporate ; 
it yields crystals of the oxalate. When pure, it is col- 
orless, melts at 124°, and boils at 322°. It is decom- 
posed by hot water into oxalic acid and wood-spirit ; 
by solution of ammonia into oxamide and wood-spirit. 

Sulphomethylic Acid (IfeO, 2S0 3 +HO) is the com- 
pound corresponding to sulphovinic acid, and is prepared 
in the same way by substituting wood-spirit for alco- 
hol. It is thus procured as a sirup, or in small crystals, 
soluble in water and alcohol. It is an instable body, 
and possesses many analogies with sulphovinic acid. 

Formic Acid (C 2 H0 3 +HO). — This acid, in the 
wood-spirit series, is the analogue of acetic acid in the 
alcohol series. It may be procured on principles similar 
to those involved in the preparation of acetic acid, as 
by the gradual oxidation of the vapor of wood-spirit in 
the air under the influence of platinum black. It may 
be prepared by the distillation of 10 parts of starch, 37 
of peroxide of manganese, 30 of water, and 30 of sul- 
phuric acid; or by distilling 10 parts of tartaric acid, 3 
of peroxide of manganese, 3 of sulphuric acid, and 3 of 
water. The dilute acid distillate is saturated with car- 
bonate of lead, and the formate of lead purified by crys- 
tallization. It is then decomposed by an equivalent of 
sulphuric acid or by sulphur e ted hydrogen. It has 
been prepared by distilling oxalic acid and glycerine at 
212°. The oxalic acid is resolved into formic and car- 
bonic acids, the glycerine remaining unchanged, 
2(HO, C 2 3 ) = (HO, C 2 H0 3 ) + 2(C0 2 ). 

Formic acid occurs naturally in the bodies of red 
ants, and hence obtained its name, having been first 
derived from the Sstillation of those animals. Anhy- 

What body does sulphomethylic acid resemble? What acid is 
formic acid the analogue of ? How is formic acid made ? Describe 
its production from oxalic acid. What is the origin of the name ? 



CHLOROFORM. 429 

drous formic acid ( C 2 II0 3 ) obviously contains the ele- 
ments of two atoms of carbonic oxide and one of water. 
It yields two hydrates, respectively containing one and 
two atoms of water. The first, for which the formula 
has already been given, is a very acrid fuming liquid, 
specific gravity 1.22, crystallizable below 32°, boiling at 
220°, and yielding an inflammable vapor whose density 
is 2.125. Formic acid is represented as the teroxide of 
Formyle (C 2 H+ 3 ) ; it yields a complete series of salts, 
and has been used as a reducing agent in photographic 
developers. 

Chloroform (C 2 ITOl 3 ) is made by distilling wood- 
spirit with a solution of chloride of lime, or chloral with 
lime and water, or a mixture of 1 part of alcohol, 24 
parts of water, and 6 parts of chloride of lime. It is a 
colorless, transparent liquid; specific gravity 1.5 ; boils 
at 140° ; the density of its vapor is 4.2. It burns with 
a green flame; is readily vaporizable; almost insoluble 
in water, but soluble in alcohol and ether ; dissolves 
resins, bromine, iodine, the alkaloids, and many other 
substances. 

When the vapor of chloroform is respired, diluted 
with air, it speedily produces insensibility, and is there- 
fore useful as an a?icesthetic in surgical operations, and 
on occasions when pain is to be avoided. It should 
never be respired by persons having affections of the 
lungs or heart, and must always be taken in ihe recum-- 
bent position, with the clothing loosened. Notwith- 
standing these precautions, death occasionally results 
from its use. 

The relation between formic acid and chloroform is 
obvious, consisting in the substitution of three atoms 
of chlorine for three of oxygen. It is regarded as the 
terchloride of formyle. There are two analogous com- 
pounds : 

Bromoform C 2 HBr 2 

Iodoform CJII 2 

Formomethylal (C 3 H^0 2 ) is prepared by distilling 
wood-spirit, oxide of manganese, and dilute sulphuric 

What compounds does formic acid yield? How is chloroform 
made? Of what use is chloroform? What precautions shpuld be 
taken in respiring it? What are the formulas for chloroform, bro- 
moform, and iodoform ? How is formomethylal prepared ? 



430 SUBSTITUTIONS IN METHYLE COMPOUNDS. 

acid. On saturating the product with potassa, formo- 
methylal separates as a colorless oily liquid, specific 
gravity .855, "boiling at 107°, and soluble in water. 

Methyle-mercaptan. — Formed like the common mer- 
captan by substituting sulphomethylate of potassa for 
sulphovinate of lime. It is analogous to common mer- 
captan. 

When chlorine is made to act on the oxide of me- 
thyle at common temperatures, it removes one of the 
hydrogen atoms, and, by continuing the action, a sec- 
ond may -be taken away, and the process of substitu- 
tion, as shown in the following series, may be carried so 
far as to end in the entire removal of the hydrogen and 
oxygen, and the production of chloride of carbon : 

Oxide ofMethyle C 2 H 3 

1st substitution C 2 H 2 0, CI 

2d " C 2 HO, Cl 2 

3d " c 2 o,a 3 

4th < ' Chloride of Carbon C 2 C/ 4 

Other methylic compounds furnish similar series, 
thus : 

Chloride of Methyle C 2 H 3 Cl 

1st substitution C 2 H 2 Cl 2 

2d " Chloroform C 2 H Cl z 

3d " Chloride of Carbon C 2 CL 



LECTURE LXXVIII. 



The Potato-Oil Group. — Amyle. — Fusel Oil. — Chlo- 
ride of Amyle. — Sidphamylie Acid. — Amylene. — 
Valerianic Acid. 

The Benzoyle Gboup. — Oil of Bitter Almonds. — 
Benzoic Acid. — Sidphobenzoic Acid. — - Chloride of 
Benzoyle. — Benzamide. — Hydrobenzamide. 

In the distillation of brandy from potatoes a volatile 
oil passes over ; it is the hydrated oxide of a compound 
radical, Amyle, C W JT U . 



What is the action of chlorine on oxide of methylal ? Give the se- 
ries resulting from the action of chlorine. What is the composition 
of am vie ? 



COMPOUNDS OF AMYLE. 431 

The Potato -Oil Group. 

Amyle, C l0 H n =Ayl 

Amylic Ether —AylO 

Amylic Alcohol (Potato Oil) =AylO+HO 

Chloride of Amyle =AylCl 

Etc. Etc. 

Amylene = C l0 H 10 

Valerianic Acid =^C 10 H 9 O 3 

Amyle is isolated by acting with zinc amalgam on 
iodide of amyle under pressure. It is a colorless, pellu- 
cid liquid, of an ethereal odor and burning taste. Cool- 
ed to 18° it thickens, but does not solidify; specific 
gravity at 52°, .1104= ; boils at 310°. It does not ignite 
at ordinary temperatures, but burns when heated ; is 
insoluble in water, but is soluble in all proportions in al- 
cohol and ether. It forms a hydride. 

Amylic Ether acts like the ethers of ethyle and me- 
thyle. 

Uydrated Oxide of Amyle — Amylic Alcohol — Potato 
Oil — Fusel Oil — passes over toward the end of the first 
distillation of potato spirit or corn spirit, and communi- 
cates to it a milky tint. On standing, it floats to the 
surface, and, may be purified by washing with water, 
drying with chloride of calcium, and redistillation at 
268°. It is a colorless liquid, of a peculiar, nauseating, 
suffocating, and persistent odor, and acrid taste ; sjDecif- 
ic gravity .812; boils at 270°, crystallizes at 4°. It is 
sparingly soluble in water, but dissolves in alcohol, ether, 
and fixed and volatile oils. When acted on by oxidiz- 
ing agents it yields Valeric acid. 

Chloride of Amyle is made by distilling equal weights 
of potato oil and perchloride of phosphorus, washing 
with potassa water, and redistilling from chloride of 
calcium. It is an aromatic liquid, boils at 215°, and 
burns with a green flame. Under the influence of sun- 
shine eight of its hydrogen atoms may be removed, eight 
chlorine atoms being substituted for them, C w H u Cl 
yielding O 10 IT 3 Cl^ forming chlorureted chloride of 
amyle. 



Mention the members of the potato-oil group. What are the 
properties of amyle ? Describe fusel oil. How is chloride of amyle 
made? What effect has chlorine on it under the influence of sun- 
shine? , 



432 DERIVATIVES OF AMYLE. 

The Iodide, and Bromide of Amyle are compounds 
analogous to the chloride. 

Acetate of the Oxide of Amyle is obtained by distil- 
ling, acetate of potassa, potato oil, and sulphuric acid. 
It is a colorless liquid, which boils at 257°. 

Sulphamylic Acid (AylO, 2S0 3 H-\-HO) is generated 
when sulphuric acid is made to act on an equal weight 
of potato oil. From this, by the successive action of 
carbonate of baryta and sulphuric acid, it may be pro- 
cured by operating on the same principles as for sul- 
phovinic acid, to which, both in constitution and prop- 
erties, it is analogous. It is a sirupy or crystalline body, 
and is decomposed by ebullition into potato oil and sul- 
phuric acid. 

Amylene is obtained by the action of anhydrous phos- 
phoric acid on potato oil. It is an oily liquid, lighter 
than water, boiling at 102°. It is a hydrocarbon, iso- 
meric with olefiant gas and etherine. The density of 
its vapor is 5.06, five times that of olefiant gas ; each 
volume of it therefore contains ten volumes of hydrogen 
and ten atoms of carbon. It has been used as an an- 
aesthetic, but has caused fatal results several times. It 
occupies the same position that olefiant gas does in the 
wine-alcohol series. 

Valerianic Acid ( C 10 IT 9 3 ) bears the same relation 
to the amyle group that acetic acid does to the wine-al- 
cohol group, or formic acid to the wood-spirit group. 
It is formed when warm potato oil is dropped on pla- 
tinum black in contact with the air. It occurs natural- 
ly in the root of the Valeriana Officinalis and other 
plants, and in train oil, but is best made by heating po- 
tato oil in a flask with a mixture of quick-lime and hy- 
drate of potassa for several hours at a temperature of 
400°. The white residue is immersed in cold water and 
distilled with a slight excess of sulphuric acid, so as to 
drive off hydrated valerianic acid and water. It is an 
oily liquid, of an acid taste, specific gravity .944, com- 
bustible, and boiling at 270°. The anhydrous acid is 
formed by the action of oxychloride of phosphorus on 

How is sulphamylic acid generated ? What are the properties of 
amylene ? What are its relations to olefiant gas ? What is the an- 
alogue of valerianic acid? How is it made ? How is anhydrous va- 
lerianic acid made ? 



THE BENZOYLE GROUP. 433 

valerate of potassa. It is a limpid oil, with a smell of 
apples, but on contact with water it is hydrated, and ac- 
quires an intense odor of valerian. 

When acted on by chlorine in the dark, and the ac- 
tion aided by heat, it gives rise to Chlorovalerisic Acid 
( G 10 S 6 Ol 3 3 +HO)) in which there has been a removal 
of three hydrogen atoms and a substitution of three of 
chlorine. Under the influence of the sunshine, by the 
same process, another hydrogen atom is removed, and 
Chlorovalerosic Acid forms (C^^Cl^O^HO). 

The Benzoyle Group. 

Benzoyle C 14 fiT 5 2 =Bz 

Hydride of Benzoyle =BzH 

Oxide of " (Benzoic Acid) =BzO 

Chloride of " = BzCl 

Etc. Etc. 

Benzoyle has been obtained as an oil by the dry dis- 
tillation of benzoate of copper. It discharges the func- 
tions of a metallic body. 

Hydride of Benzoyle ( Oil of Bitter Almonds) is ob- 
tained by the distillation of bitter almonds, from which 
the fixed oil has been expressed, with water, and arises 
from the action of the water upon Amygdaline con- 
tained in the seed. It may be purified from the hydro- 
cyanic acid it contains ; it must be agitated with milk 
of lime and protochloride of iron and redistilled. It is 
a colorless liquid, of an agreeable odor and pungent fla- 
vor, not poisonous, as it is used in cookery, slightly solu- 
ble in water, but very soluble in alcohol and ether. It 
boils at 350°, is inflammable, and oxidizes in the air into 
benzoic acid. 

Oxide of Benzoyle — Benzoic Acid — is obtained by 
sublimation from gum benzoin, a resinous exudation of 
the Styrax Benzoin, a tree growing in Sumatra, Borneo, 
and Java. It is found in the pods of vanilla. The ben- 
zoin is placed in a shallow vessel, over the top of which 
a covering of filtering paper is pasted, and this covered 
by a taller cylinder of stouter paper. On heating, the 

What effect has chlorine on it in the dark and in the sunshine ? 
How is the hydride of benzoyle made? What are the properties 
of oil of bitter almonds ? What is the source of benzoic acid ? De- 
scribe the method of preparation. 

T 



434 COMPOUNDS OF BENZOYLE. 

vapor passes through the filtering paper, and, condens- 
ing in feathery crystals in the space above, falls down 
upon the paper, and is retained by it. A better meth- 
od is to boil a mixture of the gum with hydrate of lime, 
filter, concentrate the solution, add hydrochloric acid, 
and the benzoic acid crystallizes in thin plates on cool- 
ing. It may be subsequently sublimed. 

When pure, benzoic acid has no odor, but is generally 
scented with a trace of volatile oil ; it has a sour and 
acrid taste. It melts at 250°, boils at 460°, the vapor 
having a specific gravity of 4.26, and exciting cough- 
ing. It is six times more soluble in hot than cold wa- 
ter, and is dissolved by alcohol, ether, and the fixed 
and volatile oils. The crystals contain an atom of w r a- 
ter, the equivalent being 122. It forms a series of salts, 
and is sometimes used for the separation of iron from 
other metals. 

Sulphobenzoic Acid (C u II 4: S 2 Oq+2JIO) a bibasic 
acid, formed by the action of anhydrous sulphuric acid 
upon benzoic acid, the mass being dissolved in water 
and neutralized by carbonate of baryta. By filtering, 
and adding hydrochloric acid to the hot solution, on 
cooling, the sulphobenzoate of baryta crystallizes ; it 
may be decomposed by dilute sulphuric acid. It is a 
white crystalline mass. 

Chloride of Benzoyle (Bz'Cl). — When chlorine gas 
is passed through oil of bitter almonds, hydrochloric 
acid is formed, and, after expelling the excess of chlo- 
rine by heat, chloride of benzoyle remains. It is a col- 
orless liquid, of a disagreeable odor, heavier than wa- 
ter, combustible, and decomposed by boiling water into 
benzoic and hydrochloric acids. 

Benzamide {G u H 1 N r Oo) is formed by the action of 
chloride of benzoyle on dry ammonia, the chloride of 
ammonium being removed from the resulting w T hite 
mass by cold w T ater. From a solution in boiling w r ater 
the benzamide crystallizes. It melts at 239°, and cor- 
responds in its chemical relations to oxamide. 

Hydrobenzamide ( C^H^N^). — Made by the action of 
pure oil of bitter almonds on a solution of ammonia, the 

What are the properties of benzoic acid ? Describe sulphobenzoic 
acid. What is the reaction of chlorine on oil of bitter almonds ? 
How are benzamide and hydrobenzamide formed ? 



BENZ0INE. 435 

product being washed with ether, and from its alcoholic 
solution this substance crystallizes; but when impure 
•almond oil is employed, three other compounds may be 
obtained — benzhydramide, azobenzoyle, *and nitroben- 
zoyle. 



LECTURE LXXIX. 

The Salicyle and Cinnamyle Groups. — Benzoine. — 
Benzone.- — Benzole. — Sulphobenzide. — Nitrobenzide. 
— Chlorobenzide. — Hippuric Acid. — Oil of Spiraea. 
— Salicylic Acid. — Compounds of Cinnamyle. 

Benzoine ( G 2 qS\2 ^4) i s a body isomeric with bitter 
almond oil, but inodorous and tasteless. It is found in 
the residue after purifying that oil from hydrocyanic 
acid by distillation from lime and oxide of iron, and 
may be obtained by dissolving out those bodies by hy- 
drochloric acid. It crystallizes from an alcoholic solu- 
tion, on cooling, in colorless crystals, which melt at 
248°. It dissolves in an alcoholic solution of caustic 
potassa, which, by boiling until the violet color has dis- 
appeared, furnishes benzilate of potassa, a salt from 
which benzilic acid may be obtained by hydrochloric 
acid. The constitution of Benzilic acid is ( C 2 §H ll 5 +- 
HO). 

Benzone {0 2 ^Siq0 2 ) is obtained by the distillation of 
dry benzoate of lime with a little lime at a high tem- 
perature. A red liquid passes over ; it is redistilled, 
and the liquid that comes over between 600° and 620° 
is benzone, or Benzoplienone. It crystallizes in trans- 
parent rhombic prisms, insoluble in water, soluble in 
alcohol and ether. The formation from benzoate of 
lime is thus explained : 

2(CaO, CuHiO^iCaO, C0 2 )+C m H w 2 . 

Benzine — Benzole— Phene {C l2 H^ — occurs in the 
volatile liquids condensed from coal naphtha, but is best 
obtained by distilling one part of benzoic acid with 
three of slacked lime. It is a limpid, colorless liquid, 
specific gravity .85, boils at 170°, solidifies at 40°, insol- 

How is benzoine procured? What arc its properties? What is 
the process for obtaining benzone ? Where does benzole occur ? 
What are its properties ? 



436 DERIVATIVES OF BENZINE. 

uble in water, soluble in alcohol and ether. In its for- 
mation, one equivalent of benzoic acid yields two equiv- 
alents of carbonic acid and one of benzine : 

c&h s o 3 +iio= c 12 ir e +2 co 2 . 

Sulphobenzide — Sulphobenzole (C 12 IT 5 S0 2 ) — is made 
by taking the substance which arises from the union of 
benzine with anhydrous sulphuric acid, and acting upon 
it with an excess of water. The sulphobenzide, which 
is insoluble in that liquid, may be obtained in crystals 
from its ethereal solution. It melts at 212°. From the 
acid liquid from which it has been separated hyposul- 
phobenzidic acid may be obtained. The constitution 
isC l2 H 5 S 2 0,+HO. 

JVttrobenzide — Nitrobenzole ( C l2 H b NO^ — is pro- 
duced by adding benzine to fuming nitric acid gently 
heated. It is an oily liquid, of a sweet taste, heavier than 
water, boils at 415°, and is used by perfumers and confec- 
tioners under the name of Essence of Mirbane, or bit- 
ter almonds. From it Azobenzide, C 12 H 5 ]V^ may be ob- 
tained by distillation with an alcoholic solution of caus- 
tic potassa, in the form of red crystals ; the liquid con- 
tains Aniline. Binitrobenzole, C l2 H± OqJST 2 , results from 
the action of nitric and sulphuric acids upon benzine. 
In these derivatives of benzole one and two atoms of 
hydrogen are replaced by one and two atoms of NO^. 

Chiorobenzine—Chlorobenzole ( O l2 H 6 Cl 6 ) — is formed 
by the union of benzine and chlorine in the sun's rays. 
When distilled, the solid yields hydrochloric acid and a 
liquid, Chlorobenzide (C 12 IT 3 Cl 3 ). 

Hippuric Acid {C^HqO^N^zHO) is found in the 
urine of graminivorous animals, and occurs in the urine 
of persons who have taken benzoic acid. It may be 
prepared by evaporating the fresh urine of the cow, 
and acidulating the concentrated liquor with hydrochlo- 
ric acid ; crystals of hippuric acid are deposited, which 
may be purified by dissolving in boiling alcohol. On 
cooling, colorless four-sided prisms separate; they are 
soluble in 500 parts of cold water, but are abundantly 
dissolved by boiling water and alcohol. By a high tem- 
perature and the action of dilute nitric or hydrochloric 

How are sulphobenzide and nitrobenzide made ? Give some of 
the other derivations of benzole. Where does hippuric acid natural- 
ly occur ? What are its properties ? 



THE SALICYLE GE0UP. 43 *? 

acid, it yields benzoic acid and gelatin sugar ^ or Gly ' co- 
col. It gives rise to a series of salts — the hippurates. 

The Salicyle Gkoup. 
There is contained in the bark of the willow and oth- 
er trees a bitter crystalline principle, Salicine ( C 26 ^r i8 
O u ). It may be extracted by boiling the bitter bark in 
water, and digesting the concentrated solution with ox- 
ide of lead to decolorize it, removing any dissolved lead 
by sulphureted hydrogen, and evaporating until the sal- 
icine crystallizes. It forms white needles of a bitter 
taste, much more soluble in hot than cold water. The 
solutions have a bitter taste, and are Isevo-gyrate with 
regard to polarized light. Salicine is characterized by 
the deep red color it gives with strong sulphuric acid ; 
when boiled with sulphuric acid, grape sugar is a prod- 
uct; nitric acid converts it into oxalic and carbazotic 
acids. 

The Salicyle Group. 

Salicyle, C 14 # 5 4 =Sa 

Salicylous Acid =SaH 

Iodide of Salicyle 7. = Sal 

Chloride of " =SaCl 

Etc. Etc. 

Salicylous Acid — Oil of Spiraza TJlmaris, or Meadow 
Sweet ( O u Il 5 O^H) — is prepared by distilling one part 
of salicine, one of bichromate of potassa, two and a half 
of sulphuric acid, and twenty of water, the salicine being 
dissolved in one part of the water and the acid mixed 
with the rest. The yellow oil which comes over is rec- 
tified from chloride of calcium. It may also be obtained 
by distilling the flowers of meadow-sweet with water. 
It is transparent, but turns red in the air ; is slightly sol- 
uble in water, but very soluble in alcohol ; specific grav- 
ity 1.173 ; boils at 385°; contains the same elements as 
benzoic acid. 

Salicylic Acid (C u IT 5 0±-\- 0) is obtained by the ac- 
tion of hydrate of potassa on the foregoing body by the 
assistance of heat. After the disengagement of hydro- 
gen is over, the mass is dissolved in water, and salicylic 

How is salicine obtained? Give the tests for it. What is the 
composition of oil of spiraea? How is it made? Describe salicylic 
acid. 



438 COMPOUNDS OF SALICYLE. 

acid separates in crystals on the addition of hydrochlo- 
ric acid. It is more soluble in hot than cold water, and 
is charred by hot oil of vitriol. The salicylates strike a 
violet-blue color with a persalt of iron. Certain, insects 
oxidize salicine in their bodies, and, irritated on paper 
impregnated w T ith a persalt of iron, produce violet spots. 
Oil of Winter-green is a salicylate of the oxide of rne- 
thyle. 

Chloride of Salicyle is made by the action of cjilorine 
on salicylous acid. Its crystals are insoluble in water, 
but soluble in solutions of the fixed alkalies, from which 
it separates on the addition of an acid, resisting decom- 
position even when boiled with caustic potassa. It 
unites with caustic potassa. 

Bromide and Iodide of Salicyle are not of interest. 

Chlorosamide (C 42 1I 15 J¥ 6 5 C1 3 ). — Ammoniacal gas is 
absorbed by the chloride of salicyle, producing a yellow 
body, crystallizing from a boiling ethereal solution. It 
is insoluble in water. When acted upon by hot acids 
it yields a salt of ammonia and chloride of salicyle ; an 
alkali forms with it ammonia and chloride of salicyle. 
There is an analogous bromosamide. 

Salicylide of Potassium (KST) is formed by the ac- 
tion of oil of meadow-sweet on a solution of caustic po- 
tassa. It forms in yellow crystals from its alcoholic so- 
lution, and has an alkaline reaction. 

Melanic Acid ((7 lo i^0 5 ) is produced when the crys- 
tals of salicylide of potassium are exposed in a moist 
state to the air. They first turn green and then black, 
and alcohol extracts from them melanic acid. 

ClNNAMYLE. 

The essential oil of cinnamon is supposed to be the 
nydride of a compound radical, Cinnamyle. 

The Cinnamyle Group. 
Cinnamyle, C 1Q H 7 2 — Ci 

Hydride of Cinnamyle (Oil of Cinnamon)...... = Ci H 

Oxide of " (Cinnamic Acid) — CiO 

Chloride of " = CiCl 

Etc. Etc. 

What is oil of wintergreen ? How is chlorosamide produced ? 
Describe the production of salicylide of potassium. How is melanic 
acid made ? Describe the cinnamyle group. 



THE CINNAMYLE GROUP. 439 

Hydride of Cinnamyle ( Oil of Cinnamon) is obtain- 
ed by infusing cinnamon in a solution of salt and then 
distilling the whole. It is heavier than water, and may 
be separated from that liquid by contact with chloride 
of calcium. 

Cinnamic Acid is formed when oil of cinnamon is 
exposed to oxygen, the oil becoming a white crystalline 
mass — hydrated cinnamic acid. It may also be made 
by dissolving the oil of Balsam of Tolu in an alcoholic 
solution of potassa, evaporating to dryness, dissolving 
in hot water, and adding to the cinnamate of potassa an 
excess of hydrochloric acid. It melts at 248°, and boils 
at 560°. It is soluble in boiling water and alcohol; is 
decomposed by nitric acid into oil of bitter almonds and 
benzoic acid. 

Chlorocinnose ( C^H^ Cl± 2 ) arises from oil of cinna- 
mon by the substitution of four atoms of chlorine for 
four of hydrogen, and is made by the action of chlorine 
on oil of cinnamon by the aid of heat. It crystallizes 
from its alcoholic solution in colorless needles. 

Ginnamole (6 Y 16 ^), which bears the same relation to 
cinnamic acid that benzole does to benzoic acid, is 
formed when cinnamic acid is distilled with baryta. It 
is isomeric with Styrole. 



LECTURE LXXX. 

The Nitrogenized Principles. — Ammonia and its 
Salts. — Cyanogen. — Hydrocyanic Acid.—Amygda- 
line. — Cyanide of Potassium. — Cyanic, Fulminic, 
and Cyanuric Acids. 

Ammonia. — I have already described in Lecture LVI. 
the compounds of hydrogen and nitrogen, under the 
names of amidogen, ammonia, and ammonium, and have 
also shown the relation there is between the salts of 
potassa and soda and those of the oxide of ammonium. 
This compound metal is a hypothetical body; its exist- 
How is oil of cinnamon procured? What is cinnamic acid? 
State its properties. How are chlorocinnose and cinnamole made ? 
What compounds of nitrogen and hydrogen are there? How may 
ammonium he produced ? 



440 SALTS OF AMMONIA. 

ence may, however, be illustrated by passing a Voltaic 
current through a globule of mercury in contact with 
moist chloride of ammonium, or by putting an amalgam 
of mercury and potassium in a strong solution of that 
salt. The mercury rapidly increases in volume, retain- 
ing its metallic aspect, becomes of the consistency of 
butter, with a very trivial increase of weight, the result- 
ing substance being Ammoniacal Amalgam. All at- 
tempts to insulate ammonium from it have failed. 

The most important salts of ammonia are the follow- 
ing: 

Chloride of Ammonium — Sal Ammoniac — was for- 
merly brought from Egypt, but is now made from the 
ammoniacal liquors resulting from the destructive dis- 
tillation of animal matters, coal, etc. It is soluble in 
an equal weight of boiling water, crystallizes in cubes 
or octahedrons, and sublimes below a red heat un- 
changed. It is decomposed by lime and potassa, and is 
formed when the vapors of ammonia mingle with those 
of hydrochloric acid. It is much used for tinning met- 
als in soldering. 

Nitrate of Ammonia is formed by neutralizing nitric 
acid with ammonia. It is deliquescent, and therefore 
very soluble in water. At 22° it fuses, at 356° boils, at 
400° is resolved into protoxide of nitrogen and water, 
at 600° decomposes with slight explosion. 

Carbonates of Ammonia. — The neutral carbonate 
only exists in combination. With the carbonate of wa- 
ter it> unites, forming Bicarbonate of Ammonia, which 
may be prepared by washing the commercial Sesqui- 
carbonate with water or alcohol, which leaves it undis- 
solved. The carbonate of ammonia of commerce, Salt 
of Hartshorn, is prepared by sublimation from a mix- 
ture of sal ammoniac and chalk. Its constitution is 
not uniform, though it is commonly regarded as a ses- 
quicarbonate (2JVJT 3 , 3 C0 2 , 2HO). 

Sulphate of Ammonia may be made by neutralizing 
sulphuric acid with carbonate of ammonia. It is solu- 
ble in twice its weight of cold water, and crystallizes in 
six-sided prisms. 

Can ammonium be isolated ? What are the sources of sal ammo- 
niac ? What change occurs in nitrate of ammonia at 400° ? De- 
scribe the carbonates of ammonia. 



CYANOGEN. 441 

Hydrosidphate of Ammonia — Sulphide of Ammo- 
nium — is made by passing sulphureted hydrogen into 
water of ammonia until no more is absorbed. Though 
colorless at first, it absorbs oxygen, and sulphur being 
liberated, it turns yellow. It is of considerable use as 
a test for metals. 

Cyanogen — Bicarburet of Nitrogen (C 2 N). — The 
mode of preparing this remarkable body, and also its 
leading properties, have been described in Lecture LVI. 
It is of great interest in organic chemistry, as being the 
first distinctly-established compound radical, and the 
best representative of the electro-negative class of t'hose 
€>odies. 

We may call to mind that it is easily made by the 
decomposition of cyanide of mercury at a low red heat, 
is a condensible gaseous body, soluble in water, and 
therefore must be collected over mercury. It is com- 
bustible, and burns with a purple flame. 

The Cyanogen Group, 

Cyanogen. CJSf Cy 

Hydrocyanic Acid CyH 

Cyanic Acid CyO 

Fnlminic Acid Oy 2 2 

Cyanuric Acid Cy 3 3 

Etc. Etc. 

Paracyaiiogen (C±N 2 ). — When the cyanide of mer- 
cury is decomposed in the process for preparing cyano- 
gen, a brownish substance is set free, which is paracy- 
anogen. It is insoluble in water and alcohol, and is poi 
ymeric with cyanogen. 

Hydrocyanic Acid — JPrussic Acid — Cyanide of Hy- 
drogen — may be obtained in a state of purity by pass- 
ing dry sulphureted hydrogen over dry cyanide of mer- 
cury in a tube, and conducting the vapor which is 
evolved when the tube is warmed into a vial immersed 
in a freezing mixture. The result of the decomposition 
is sulphide of mercury and hydrocyanic acid. In a 
state of aqueous solution, it is best obtained by the ac- 
tion of dilute sulphuric acid on ferrocyanide of potassi- 

How is hydrosulphate of ammonia made? What is the composi- 
tion of cyanogen ? Why is it of interest ? Name some members of 
the cyanogen group. What is paraoyanogen ? How is hydrocyanic 
acid made? Give another method. 

T2 



442 PKUSSIC ACID. 

urn in a retort, and receiving the vapor in a Liebig's 
condenser. Having ascertained the strength of the 
product, it may then be diluted to the proper point. 
This examination may be conducted by precipitating a 
known weight of the acid with nitrate of silver in ex- 
cess, collecting the cyanide of silver on a weighed fil- 
ter, washing, drying, and re weighing, which gives the 
weight of the cyanide. This, divided by five, is the 
weight of the pure hydrocyanic acid nearly. 

Anhydrous hydrocyanic acid is a colorless and very 
volatile liquid, which exhales a strong odor of peach- 
blooms; specific gravity .696; boils at 80°, congeals at 
4°. It mixes with water and alcohol in any proportion* 
A drop of it held in the air on a glass rod becomes so- 
lidified by the rapid evaporation from its surface. In 
the sunlight it decomposes rapidly, producing a dark- 
colored substance; the same change goes, on, though 
more slowly, in the dark. It is one of the most insidi- 
ous and terrible poisons, a few drops producing 4eath 
in a few seconds ; and its vapor, even largely diluted 
with air, brings on very unpleasant symptoms. Under 
the action of strong acids it is decomposed into ammo- 
nia and formic acid, the change being very simple : 
C 2 N,H+3HO=]¥If 3 + C 2 H0 3 . 

Under such circumstances, hydrocyanic acid yields 
chloride of ammonium and hydrated formic acid. Hy- 
drocyanic acid may to a certain extent be preserved 
from spontaneous change by the presence of a minute 
quantity of any mineral acid. 

Prussic acid may be detected by its smell, and by 
yielding a precipitate of Prussian blue when acted upon 
in solution successively by sulphate of iron, potassa, and 
an excess of hydrochloric acid. The liquid in w T hich the 
poison is suspected to exist should be acidulated with 
sulphuric acid and distilled : the hydrocyanic acid will 
be found in the first portions which come over. 

Amygdaline ( C^H 21 22 lSr), a crystallizable substance 
found in bitter almonds, the leaves and berries of the 
cherry laurel, and the kernels of peaches, etc., is of con- 
siderable interest in connection with hydrocyanic acid, 

What are the properties of hydrocyanic acid? What effect has it 
on animals? How may prussic acid be detected? What are the 
sources of amygdaline ? 



AMYGDALINE. 443 

inasmuch as these organic bodies yield, when distilled 
with water, that substance. The change consists in the 
action of water upon araygdaline by the aid of an azo- 
tized ferment called Synaptase .or Emidsine^ which con- 
stitutes the larger portion of the pulp of almonds ; the 
bitter almond oil at the same time makes its appearance. 
Amygdaline may be extracted from the paste of bitter 
almonds when the fixed oil has been expressed by the 
aid of boiling alcohol. The alcohol being subsequently 
distilled off, the sugar contained in the sirupy residue is 
destroyed by fermentation with yeast. The liquid, be- 
ing evaporated again to a sirup, is mixed with alcohol, 
which precipitates the amygdaline as a white crystalline 
powder, purified by being redissolved in alcohol and left 
to cool. It is soluble in hot and cold water, but sparing- 
ly soluble in cold alcohol. A weak solution of it in wa- 
ter, under the influence of a small quantity of an emul- 
sion of sweet almonds, yields at once oil of bitter al- 
monds and hydrocyanic acid; sugar and formic acid are 
also produced. When amygdaline is boiled with an al- 
kali it gives rise to Amygdalic Acid, which forms a salt 
with the alkali, and ammonia is evolved. 

Cyanide of Potassium may be formed by the direct 
union of cyanogen and potassium, or by the ignition of 
the ferrocyanide of potassium in a close vessel. For 
common purposes in the arts it may be formed in a state 
somewhat impure by mixing eight parts of ferrocyanide 
of potassium, rendered anhydrous by heat, with three 
parts of carbonate of potassa, also dry, and fusing the 
mixture in a crucible, stirring it until the fluid part of 
the mass is colorless. The sediment of iron, etc., is al- 
lowed to settle and the clear liquid poured off: it is the 
substance in question, mixed with cyanate of potassa. 
2(K 2 FeCyi+2{KO, C0 2 )=b{KCy)+KO, CyO+Fe 2 

+ 2C0 2 . 
The formation of the cyanate maybe prevented by add- 
ing to the mixture, before fusing, one eighth its weight 
of powdered charcoal ; the fused mass may then be di- 
gested in boiling alcohol, from which the cyanide crys- 
tallizes on cooling. 

Cyanide of potassium is very soluble in water, yields 

What ferment is found in almonds? What are the properties of 
amygdaline ? How is cyanide of potassium made ? 



444 CYANIC, FULMINIC, AND CYANUKIC ACIDS. 

colorless octahedral crystals which deliquesce in the air, 
melts without change at a red heat, and exhales the 
odor of prussic acid. It is very poisdfcous, and is use- 
ful as a reducing agent in mineral analysis, and as a sol- 
vent for bromide and iodide of silver in photographic 
operations. 

Cyanide of Mercury may be made by dissolving red 
oxide of mercury in hydrocyanic acid, or by the action 
of a solution of ferrocyanide of potassium on persulphate 
of mercury, the cyanide crystallizing from the filtered 
hot solution. It forms fine prismatic crystals, soluble in 
eight parts of water at 60°, and sparingly soluble in al- 
cohol. It is poisonous, and, when decomposed at a low 
red heat, yields cyanogen gas. 

Cyanic Acid (CyO+JIO) is procured by heating in 
an air-tight retort cyanuric acid deprived of its water 
of crystallization. A colorless liquid comes over into 
the receiver ; it is hydrated cyanic acid, and has a strong 
odor like acetic acid; is intensely corrosive, and produces 
blisters on the skin. It is decomposed by contact with 
water, carbonic acid being evolved ; carbonate and cy- 
anate of ammonia are formed, and, by evaporation, crys- 
tals of urea may be obtained. Cyanic acid is a very un- 
stable body, spontaneously changing in a short time into 
Cyamelide, a body of the same constitution, but a w T hite 
opaque solid, insoluble in water and alcohol, and decom- 
posed by hot oil of vitriol into sulphate of ammonia, 
w r hile carbonic acid escapes. 

Fulminic Acid ( Cy 2 2 ) has not yet been isolated, but 
some of its salts, presently to be described, are charac- 
terized by the violence with which they detonate under 
very trivial disturbances. It is a bibasic acid. 

Cyanuric Acid (Cy 3 3 -}-dIlO) may be made by 
heating urea, which disengages ammonia ; the residue 
is dissolved in hot sulphuric acid, and nitric acid added 
until the liquid becomes colorless; on mixing it with 
w r ater and allowing it to cool, the cyanuric acid sepa- 
rates. Its crystals are efflorescent ; it is sparingly solu- 

What substances result from the decomposityon ? What use is 
made of cyanide of potassium ? How is cyanide of mercury made ? 
Give the process for procuring cyanic acid. What is the character- 
istic of the fulminates ? How is cyanuric acid made ? What are its 
properties ? 



CYANATES AND FULMINATES. 445 

ble in water, and is a tribasic acid ; and, as has already 
been stated, at a red heat may be distilled, yielding cy- 
anic acid without any other product. 



LECTURE LXXXI. 

Bodies allied to Cyanogen. — Salts of the Oxycyano- 
gen Acids. — Ferrocyanogen. — Prussiate of Potas- 
sa. — Prussian Blue. — Ferricyanogen. — Ferricyan- 
ide of Potassium. — Cobaltocyanogen. — Sulphocy- 
anogen. — Sulphocyanide of Potassium. — Melam. 

Cyanate of Potassa {KO, Cy 0) may be prepared 
by oxidizing cyanide of potassium by oxide of lead in 
an earthen crucible. The result, boiled with alcohol, 
yields, on cooling, crystals of cyanate of potassa in thin 
transparent plates, which undergo no change in dry air, 
but with moisture become converted into bicarbonate 
of potassa and ammonia. 

Cyanate of Ammonia — Urea ( C 2 II 4 JV 2 2 ). — The va- 
por of hydrated cyanic acid, mixed with ammoniacal 
gas, yields cyanate of ammonia. The solution in wa- 
ter, when heated, gives off ammonia, and the cyanate 
changes into Urea, from which caustic alkalies can not 
disengage ammonia. Urea may also be made from the 
action of sulphate of ammonia on cyanate of potassa. 

Fulminate of Silver (2Ag O, C±N~ 2 2 ) is made by 
dissolving silver in warm nitric acid, and adding alco- 
hol. It separates from the hot liquid as a white pow- 
der, which, being washed in water, is dried in small 
portions, at a temperature of 100°, on filtering paper. 
It detonates with wonderful violence when either struck 
or rubbed. It is sparingly soluble in hot water, and 
crystallizes from that solution on cooling. It yields, by 
digestion with water and metals, salts, as those of zinc 
and copper. 

Fulminate of Mercury (2HgO, C 4 JV 2 2 ) is prepared 
in the same manner as the foregoing, and, like it, is very 
explosive. It is used for making percussion caps. The 

How is cyanate of potassa made ? What is the relation between 
cyanate of ammonia and urea? How is fulminate of silver made ? 
What peculiarities has it? What use is made of the fulminate of 
mercurv ? 



446 FERROCYANOGEN. 

gases evolved by its explosion are carbonic acid, nitro- 
gen, and the vapor of mercury. 

Chloride of Cyanogen ( Cy CI) is prepared by the ac- 
tion of chlorine on moist cyanide of mercury in the 
dark. It is a colorless gas, soluble in water, specific 
gravity 1.1244, congeals at 0°, boils at 11°, condenses 
into a liquid under a pressure of four atmospheres. A 
liquid compound, Cy 2 Cl 2 , is obtained from the same 
substances under the action of sunlight ; it is a heavy, 
yellow, oily liquid, insoluble in water, but soluble in al- 
cohol. The solid chloride is procured by adding hydro- 
cyanic acid to dry chlorine, and exposing to the sun- 
shine. These compounds are deadly poisons. 

Ferrocyanogen. 

Ferrocyanogen ( C 6 JSr 3 Fe = Cfy or Fey ) is a com- 
pound radical, in which iron is an important constituent. 

Hydroferrocyanic Acid ( Cfy, H 2 ) may be obtained 
by decomposing the insoluble ferrocyanide of lead by 
sulphureted hydrogen while suspended in water. The 
solution, being filtered, is to be evaporated with sulphu- 
ric acid in vacuo until the acid is left solid. It may also 
be prepared by dissolving tartaric acid in alcohol, and 
pouring it into an aqueous solution of ferrocyanide of 
potassium, the acid separating on evaporation in small 
crystals. Another method consists in adding hydro- 
chloric acid to a strong solution of ferrocyanide of po- 
tassium, and then mixing it with ether, which precipi- 
tates the acid. It is soluble in water, to which it gives 
a powerful acid reaction. It decomposes the alkaline 
carbonates with effervescence, forming ferrocyanides of 
their bases ; is inodorous, and not poisonous ; is perma- 
nent in the dry state, but, moistened and exposed to air, 
forms Prussian blue. 

Ferrocyanide of Potassium — Prussiate of Potassa 
(2iT, Cfy+SHO). — This salt is made on the large scale 
by igniting carbonate of potassa, iron filings, and ani- 
mal matter in an iron vessel. The mass is then acted 
on by hot water, dissolving out a large quantity of cy- 

What are the properties of chloride of cyanogen ? What is the 
composition of ferrocyanogen ? How may hydroferrocyanic acid be 
made ? What change occurs in it when exposed to air ? Give the 

process for making prussiate of potassa. 



PRUSSIAN BLUE. 447 

anide of potassium, which is converted into the ferrocy- 
anide by the iron. The filtered solution, on cooling, 
yields lemon-yellow crystals, soluble in four parts of 
cold water. It is not poisonous. At a red heat it de- 
composes, cyanide of potassium forming. It is a valua- 
ble reagent, forming insoluble precipitates in many me- 
tallic solutions: white with the salts of manganese, zinc, 
tin, cadmium, lead, bismuth, antimony, protosalts of 
iron, mercury, and silver ; yellowish-green with those of 
cobalt ; reddish-broion with those of copper and urani- 
um ; blue with the persalts of iron ; pea-green with the 
salts of nickel. 

Common Prussian Blue (SCfy+4Fe) is prepared 
by precipitating a persalt of iron by solution of ferro- 
cyanide of potassium. When dry, it is of a deep blue 
color, with a lustre of coppery-red. It is insoluble in 
water ; is decomposed by alkaline solutions, which yield 
alkaline ferrocyanide, and precipitate oxide of iron. It 
is soluble in solution of oxalic acid, and then constitutes 
the basis of blue writing inks. It is also much em- 
ployed as a paint. 

Basic Prussian Blue (3Cfy, 4Fe+Fe0 3 ) is formed 
when the white precipitate yielded by a protosalt of 
iron with ferrocyanide of potassium is exposed to the 
air. As its formula shows, it is common Prussian blue 
with peroxide of iron. It differs from Prussian blue in 
the remarkable peculiarity that it is soluble in water. 

FERRICYAlSrOGEN. 

Ferricyanogen — Ferridcyanogen (C 12 W 6 Fe 2 =: Cfdy, 
or Fdey) — is a hypothetical compound radical, which 
yields some compounds of interest. 

Ferricyanide of Potassium (3iT+ Cfdy) may be 
made by passing chlorine through a dilute solution of 
ferrocyanide of potassium until it ceases to yield a pre- 
cipitate with a persalt of iron. The liquid, being con- 
centrated, produces, on cooling, deep red crystals, the 
solution of which is of a greenish color. It gives no 
precipitate with peroxide of iron, but with the proto- 
salts a bright blue, lighter than Prussian blue, and 
known as Turnbull's blue. 

What are the properties of prussiate of potassa? What precipi- 
tates does it yield ? How is Prussian blue made ? What is basic 
Prussian blue? How is ferricyanide of potassium made ? 



448 SULPH0CYAN0GEN. 

Cobaltocyanogen (Cy Q Co 2 — GJcy) is analogous to 
ferricyanogen in composition, and, like it, is tribasic. 

Sulphocyanogen (G 2 JVS 2 = Csy) is obtained by sat- 
urating a concentrated solution of sulphocyanide of po- 
tassium with chlorine, as well as by boiling a soluble 
metallic sulphocyanide in diluted nitric acid. It falls in 
the form of a yellow precipitate, which preserves its 
color when dry; is insoluble in water, alcohol, and ether, 
but soluble in hyposulphuric acid. 

Sidphocycmic Acid — Hydrosulphocyanic Acid (Cy 
S 2 H) — may be obtained by decomposing sulphocya- 
nide of lead by dilute sulphuric acid, taking care to 
leave excess of the salt of lead, which may afterward 
be removed by sulphureted hydrogen. It is also form- 
ed when sulphocyanide of lead or silver is decomposed 
by sulphureted hydrogen. The hydrated acid is color- 
less, decomposed by exposure to air or heat, yields 
with the peroxide of iron a blood-red color, and exists 
in the saliva of man and the sheep. 

Sulphocyanide of Potassium (IT Csy) may be made 
by heating powdered ferrocyanide of potassium with 
half its weight of sulphur and one third of carbonate 
of potassa, and keeping it melted for a short time. 
The mass is then boiled with water, which dissolves out 
the sulphocyanide, and the solution, being concentrated, 
yields prismatic crystals of the salt. It is soluble in 
water and alcohol, and deliquesces in the air ; melts at 
a red heat ; its solution with peroxide of iron gives a 
blood-red color. 

Melam ( C 12 3'qN 11 ) is produced when sulphocyanide 
of ammonium is distilled at a high temperature, or by 
heating dry sulphocyanide of potassium with twice its 
weight of sal ammoniac. It is insoluble in water, but 
dissolves in strong sulphuric acid. When heated, it 
yields mellone and ammonia. 

Melamine (C 6 IT 6 ]¥ 6 ), Ammelin ((7 6 iV^iZ" 5 2 ), and 
Ammelid (C 12 JVqHq0 6 ) are products of the decomposi- 
tion of melam. 

What precipitates does ferricyanide of potassium yield ? How is 
sulphocyanogen made? Describe the production of sulphocyanic 
acid. What precipitate does sulphocyanide of potassium yield? 
When does melam arise ? What products arise from the decompo- 
sition of melam ? 



MELLONE — UREA. 449 



LECTURE LXXXIL 



Mellone. — Urea. — Mellone. — Mellonides of Hydro- 
gen and Potassium. — Natural and Artificial Forma- 
tion of Urea. — Uric Acid. — Its Derivatives. — Mu- 
rexide. — Xanthic and Cystic Oxides. 

Mellone (C^^Me). — If sulphocyanide of potas- 
sium be acted upon by chlorine or nitric acid, a yellow 
powder is deposited. This, when heated, gives off bi- 
sulphide of carbon and sulphur, and there is left a yel- 
lowish powder, which is mellone. The relation of its 
constitution with cyanogen is obvious. It resists a 
moderate heat without change, and combines directly 
with metals to form Mellonides. 

Hydromellonic Acid (MeH 3 ).- — By adding hydro- 
chloric acid to a hot solution of mellonide of potassium, 
this acid separates as a white powder on cooling. It is 
partly soluble in hot water, and possesses strong acid 
powers. 

Mellonide- of Potassium (MeIC 3 ) may be prepared 
by melting ferrocyanide of potassium with half its 
weight of sulphur, and adding, when the fusion is com- 
plete, five per cent, of dry carbonate of potassa. The 
resulting mass is acted on by water, and the solution, 
being filtered, is evaporated until, on cooling, it forms 
a mass of crystals, from which the sulphocyanide may 
be removed by alcohol, and the mellonide left. It is 
soluble in water, and yields, by double decomposition 
with the salts of baryta, lime, etc., mellonides of these 
bodies, for the most part sparingly soluble. 

Urea (C 2 H 4r 2 JS 7 2) may be obtained from urine by 
adding to it, when concentrated, a strong solution of 
oxalic acid. The precipitated oxalate of urea is to be 
boiled with powdered chalk, and the filtered solution 
concentrated until the urea crystallizes on cooling. It 
may also be made artificially by adding to a strong so- 
lution of cyanate of potassa an equal weight of dry sul- 

What relation does mellone bear to cyanogen? How is hydro- 
mellonic acid made? How is mellonide of potassium prepared? 
How is urea obtained from urine ? How may it be made artificially ? 



450 UREA. — URIC ACID. 

phate of ammonia ; the solution is evaporated to dry- 
ness in a water-bath, and the urea dissolved out by al- 
cohol. It crystallizes in prisms, very soluble in water, 
but permanent in the air. At a high temperature it 
gives off ammonia and cyanate of ammonia, cyanuric 
acid remaining. Urea contains the elements of cyanate 
of oxide of ammonium, has neither an acid nor alkaline 
reaction, is decomposed by hot alkaline solutions with 
evolution of ammonia, and by uniting with two atoms 
of water yields carbonate of ammonia, a result which 
takes place during the putrefaction of urine, the change 
being brought on by a nitrogenized ferment — the mu- 
cus of the bladder. Urea unites with acids, and forms, 
with nitric and oxalic acids, characteristic salts. Ac- 
cording to Dr. J. C. Draper, it arises principally from 
the excess of nitrogenized matter taken into the sys- 
tem. 

Uric Acid — Lithic Acid ( C^H^JV^ 6 ) — may be ob- 
tained from the solid urine of serpents, which, being 
boiled in solution of caustic, potassa and filtered, yields 
uric acid by the addition of hydrochloric acid, as a 
white, inodorous, and sparingly soluble powder, soluble 
without change in sulphuric acid, from which it is pre- 
cipitated by water. Uric acid also exists in human 
urine, and appears to be always a product of the action 
of the animal economy. It may be precipitated by add- 
ing hydrochloric acid, and allowing the urine to stand 
twenty-four hours. Of its salts the urate of soda is in- 
teresting; it is the chief ingredient of gouty concretions 
in the joints, called chalk-stones. The urate of ammonia 
occurs as a urinary calculus, and is often deposited from 
urine as a reddish cloud or powder. Guano, the excre- 
ment of aquatic birds, contains a large proportion of 
uric acid. 

Allantoin ( CJS^ N~ 2 3 ) is prepared by boiling uric 
acid with peroxide of lead ; the filtered solution, being 
concentrated, deposits prismatic crystals of allantoin on 
cooling. It is soluble in 160 parts of cold water. By 
a solution of caustic alkali it is decomposed into ammo- 
nia and oxalic acid, assuming during this change the 
elements of three atoms of water. 

What are the properties of urea ? What is the source of uric acid ? 
What are chalk-stones ? How is allantoin prepared ? 



ALLOXAN. 451 

Alloxan ( CqJS^JV^ O 10 ) is made by the action of con- 
centrated nitric acid on uric acid in the cold. The uric 
acid is to be added in small portions successively until 
about one third the weight of the nitric acid has been 
used. An effervescence takes place, nitrogen and car- 
bonic acid are evolved, and there is left a white mass, 
from which the excess of acid is to be drained. The 
substance is then to be dissolved in hot water and crys- 
tallized. Its solution has an acid reaction and a bitter 
taste, and stains the skin purple, and with a protosalt 
of iron and an alkali yields a characteristic blue com- 
pound. If the nitric acid be very dilute, Alloxantin 
(<7 8 J5T 5 i^O 10 ) arises. 

Alloxcmic Acid (C^ffNO^+HO) may be prepared 
by decomposing the alloxanate of baryta by dilute sul- 
phuric acid. The alloxanate itself is obtained by the 
addition of barytic water to a warm solution of alloxan. 
It is a strong acid, decomposing carbonates, and even 
water, by the aid of zinc. 

Mesoxalic Acid (C 3 4: +2S'0) may be obtained by 
boiling a solution of alloxan with acetate of lead, the re- 
sulting mesoxalate of lead being decomposed by sul- 
phureted hydrogen. It is a strong acid, resists a boil- 
ing heat, and is bibasic. 

MyJcomelinic Acid ( G Q JV 4c ir 5 5 ) is prepared by boil- 
ing a solution of alloxan with an excess of ammonia, 
and then precipitating by an excess of dilute sulphuric 
acid. It is a light yellow powder. 

Parabanic Acid ( CqH 2 O q N~ 2 ) is formed by the action 
of strong nitric acid on alloxan or uric acid by the aid 
of heat. The crystals form on cooling, and may be dried 
by draining and then reQrystallized. It is soluble in 
water, reddens litmus, and forms beautiful prismatic 
crystals. 

Oxaluric Acid ( C % H± Q N 2 ) may be made by decom- 
posing a hot solution of the oxalurate of ammonia by 
dilute sulphuric acid and cooling rapidly. The ammo- 
nia salt is itself procured by boiling a solution of the 
parabonate of ammonia, when it crystallizes, on cooling, 
in small needles. Oxaluric acid is a white crystalline 
powder. It contains the element of one atom of para- 
Give the process for making alloxan. How is alloxanic acid 
made? How are mykomelinic, parabanic, and oxaluric acids made ? 



452 URAMILE. MUREXIDE. 

bonic acid and three of water, and its solution by boil- 
ing yields oxalic acid and oxalate of urea. 

Thionuric Acid (C Q H 1 ]S T 3 S 2 O u ), a bibasic acid, pre- 
pared by decomposing thionurate of lead with sulphu- 
reted hydrogen. It contains the elements of one atom 
of alloxan, one of ammonia, and two of sulphurous acid. 

Uramile {CqH^OqJST^). — When an excess of saturated 
solution of sulphurous acid in water is mixed with a 
cold solution of alloxan, and an excess of carbonate of 
ammonia with caustic ammonia added, and the whole 
boiled, the thionurate of ammonia is deposited on cool- 
ing. From this the lead salt used in the preparation 
of the foregoing acid may be obtained by acetate of 
lead. The thionurate of ammonia, with a little hydro- 
chloric acid, being boiled in a flask, there separates a 
white body, which is uramile. It differs from thionuric 
acid in not containing the elements of two atoms of sul- 
phuric acid. If the thionurate of ammonia is mixed 
with dilute sulphuric acid and evaporated in a water- 
bath, Uramilic Acid ( C lQ H 1Q ]SF 5 15 ) is deposited. 

Micrexide — Purpurate of Ammonia — may be made 
by the action of dilute nitric acid on uric acid, and then 
adding ammonia ; or by boiling equal weights of ura- 
mile and red oxide of mercury with eighty times their 
weight of water rendered alkaline by ammonia. The 
liquid turns of a deep purple color, and, when filtered, 
deposits, on cooling, crystals of murexide in square 
prisms, which by reflected light are of a green metallic 
lustre, and by transmitted light of a purple. It is spar* 
ingly soluble in cold water, but much more so in hot, 
and is one of the most splendid colors known. It is 
made largely from guano, to be used as a dye pigment. 

Marexan — Purpuric Acid. — Murexide is to be dis- 
solved in a solution of caustic potassa, and dilute sul- 
phuric acid added. It forms a yellow powder, and, dis- 
solved in ammonia, gives rise to the foregoing body. 

Xanthic Oxide ( C±H 2 ^2 ^2) occurs as a urinary cal- 
culus of a brown color and waxy aspect. The calcu- 
lus may be dissolved in dilute potassa, and xanthic ox- 

What is the composition of thionuric acid? How is uramile pre- 
pared? How does it differ from thionuric acid? When does mu- 
rexide arise ? What is its composition ? Of what value is it ? How 
is xanthic oxide made ? 



THE VEGETABLE ACIDS. 



453 



Me precipitates as a white powder by carbonic acid. It 
is a waxy body. 

Cystic Oxide ( C 6 JI 6 J^S 2 4 ) occurs also as a urinary 
calculus. It is remarkable for the large quantity of sul- 
phur it contains. 



LECTURE LXXXIII. 

The Vegetable Acids. — Tartaric Acid and its Salts. 
— Citric Acid. — Tannic Acid. — Gallic Acid. — JPyro- 
gallic Acid. — Metagallic Acid. 

Of the vegetable acids, several will be described, with 
their associated alkalies. The following are treated of 
in this Lecture : 



Maleic C s H0 5 +2HO 

Fumaric CJ10 3 + HO 

Tannic C lQ H 5 9 +3HO 

Gallic C 1 H0 3 -\-2HO 

Ellagic C 7 # 2 4 

Pyrogallic C 6 H 3 3 

Metagallic C G H 2 2 



Tartaric C 8 H±O 10 +2FI0 

Paratartaric..C 3 # 4 lo +2HO 
Pyrotartaric..(7 6 iy 3 5 + HO 
Tartralic....,..C r 8 # 4 1() +3HO 

Tartrelic C 8 H^O 10 + HO 

Citric C l2 H 5 O u +ZHO 

Aconitic C i H0 3 + HO 

Malic... ...0 s il 4 8 +2HO 

Besides acids such as these, which constitute a very 
numerous group, there is another class, which pass un- 
der the name of Coupled Acids , the peculiarity of which 
is that they consist of an acid affixed or coupled to an- 
other body, which, without affecting the neutralizing 
power of the acid, accompanies it in all its combina- 
tions. Thus hyposulphuric acid couples with naptha- 
line to form hyposulphonapthalic acid, which neutral- 
izes just as much of any base as hyposulphuric acid 
could do, the napthaline not changing its powers. 

Tartaric Acid (CqH^Ojq+2110). — A bibasic acid, 
which occurs, as has already been stated, in the juice 
of grapes and other fruits as bitartrate of potassa. It 
may be obtained by dissolving cream of tartar in boil- 
ing water and adding powdered chalk, a tartrate of lime 
precipitating. The rest of the tartaric acid may be ob- 
tained from the solution by the addition of chloride of 

How is cystic oxide made ? Name some of the vegetable acids, 
and give their composition. What are coupled acids? Give an ex- 
ample. Describe tartaric acid. 



454 SALTS OF TARTARIC ACID. 

calcium, which yields another portion of tartrate of lime, 
and may be decomposed by digesting with an equiva- 
lent proportion of dilute sulphuric acid. The concen- 
trated and filtered solution yields crystals acid to the 
taste, inodorous, and soluble both in water and alcohol. 
The solution decomposes by keeping. Tartaric acid 
gives several valuable salts. 

Tartrate ofPotassa — Soluble Tartar (2KO, C S H 4 O w ) 
— may be made by adding carbonate of potassa to cream 
of tartar. It is very soluble, and is useful as an aperient. 

Bitartrate of Potassa — Cream of Tartar (KO, HO, 
CqIT^Ow) — is the salt deposited from the juice of the 
grape during fermentation as Argol. It may be puri- 
fied from the coloring matter it contains by solution in 
hot water and the action of animal charcoal. In cold 
water it is very sparingly soluble. It produces black 
flux when ignited in a close vessel, the black flux being 
carbonate of potassa enveloped in carbonaceous matter. 

Tartrate of Potassa and Soda — Pochette Salt — Salts 
of Seignette {KO,NaO, 0^0^+8110) — may be 
procured by neutralizing a solution »of the foregoing 
salt with carbonate of soda. On evaporation and cool- 
ing, it separates in large prismatic crystals. It possess- 
es the property of causing the deposit of metallic silver 
on glass from solutions of the ammoniacal nitrate of sil- 
ver, and has been much used by the author in the mak- 
ing of silvered glass sj)ecula for his reflecting tele- 
scope at Hastings. 

Tartrate of Antimony and Potassa— Tartar Emetic 
[KOSbOn t\H±O m +HO). — This valuable medicinal 
agent is made by boiling oxide of antimony in a solu- 
tion of cream of tartar ; on cooling, the crystals are de- 
posited. They are much more soluble in hot than in 
cold water, and dissolve without decomposition. It has 
emetic and alterative qualities, and is poisonous in large 
doses. 

Paratartaric Acid — Pacemic Acid — has the same 
constitution as tartaric acid, and resembles it very close- 
ly, being found in the grapes of certain parts of Ger- 
many and France. Racemic acid, however, differs from 

What is argol? What is the difference between soluble tartar 
and cream of tartar? What is the composition of RochelJe salt? 
What peculiar property has it ? Give the formula for tartar emetic. 



TARTARIC AND CITRIC ACIDS. 455 

tartaric in yielding a precipitate with a neutral salt of 
lime. 

JPyrotartaric Acid (C 6 IT 3 5 -\-irO) is obtained by 
the destructive distillation of tartaric acid at 400°, as a 
liquid. 

The action of heat on tartaric acid is remarkable. 
When exposed to a temperature approaching 400° it 
melts, throws off water, and yields in succession the fol- 
lowing group : 

Crystallized Tartaric Acid C s H±O lQ +2HO 

Metatartaric Acid C b H±O lQ -\-2HO 

Isotartaric Acid C^H^O^ + HO 

Tartralic Acid 2(C s H±O 10 )+SHO 

Tartrelic Acid C s H^O 10 + HO 

Anhydrous Tartaric Acid C Q H^ O x 

All these, by the continued contact of water, pass back 
into the condition of tartaric acid. 

Citric Acid ( C^H b O^ + ZHO), a tribasic acid occur- 
ring abundantly in the juice of lemons and other sour 
fruits, and separated therefrom by the aid of chalk 
and sulphuric acid. It is clarified by digestion with an- 
imal charcoal, and yields prismatic crystals of a pleasant 
taste, and soluble in both hot and cold water. The 
crystals are of two different forms, according to the 
conditions of their formation : those which separate in 
the cold by spontaneous evaporation contain five atoms 
of water, three of which are basic ; but those which are 
deposited from a hot solution contain only four. 

The citrates form a very numerous family of salts ; 
for, as the acid is tribasic, we have them with three at- 
oms of metallic oxide, or two of oxide and one of wa- 
ter, or one of oxide and two of water, besides subsalts. 

Aconitic Acid — JEJquisetic Acid (C 12 If 6 } 2+J^O) — 
is formed by fusing citric acid and dissolving the result- 
ing brown product in water, the change being 

O u II 8 O u = C 12 K 6 6> 12 + 2 HO ; _ 
that is, one atom of hydrated citric acid yields one of 
aconitic acid and two of water. Aconitic acid occurs 
naturally in the varieties of aconite and in the equise- 
tums. Itaconic and Citraconic Acids are produced 

Describe the action of heat on tartaric acid. What is the source 
of citric acid? What crystalline forms has it? How may aconitic 
acid be formed ? 



456 MALIC AND TANNIC ACIDS. 

by the continued influence of heat; their formula is 

c 10 n,o 6 +2iro. 

Malic Acid (C 8 H 4r O Q +2JETO)^ a bibasic acid occur- 
ring in the juice of apples and other fruits. It may also 
be prepared from the stalks of rhubarb, in which it is 
found with oxalate of potassa. It is a colorless solid, 
soluble in water, the solution changing by teeping. 
When heated in a retort to 400°, it melts and then boils, 
emitting a volatile acid, Maleic Acid (C 8 IT 2 6 +2irO), 
which condenses with water in the receiver. . If the 
heat be carefully maintained between 270° and 280°, 
the product is Fumaric or JParamaleic Acid, which is 
isomeric with maleic, and also aconitic acid. 

Tannic Acid (654^22^34)5 an astringent principle 
Fig. 307. found in the bark of the oak, nut-galls, and 
other vegetable productions. It may be 
separated by placing in a vessel, 5, Fig. 307, 
powdered galls. On pouring on them sul- 
phuric ether containing ten per cent, of wa- 
ter, a liquid drops through the funnel tube, 
c, into the bottle, a, spontaneously separa- 
ting into two portions. The lower, which is 
a solution of tannic acid in water, is to be 
decanted and evaporated in the presence of 
sulphuric acid in vacuo. It yields tannic 
acid, or tannin, in the form of an uncrystal- 
lized mass. This acid is soluble in water, 
but much less so in ether, has an astringent 
taste, and reddens litmus paper. With the persalts of 
iron, it gives a characteristic and valuable precipitate 
of a black color, the basis of common writing ink. The 
following furnishes a good waiting ink. Digest three 
quarters of a pound of bruised galls in a gallon of cold 
water, then add six ounces of sulphate of iron, with an 
equal weight of gum arabic, and a few drops of crea- 
sote. Let the mixture digest for two or three weeks, 
with occasional agitation, then decant. Tannic acid 
forms insoluble compounds with starch, gelatine, and 
other organic bodies, that with gelatine being of con- 
siderable interest : it is the basis of leather. From the 

Where does malic acid occur? What effect has heat on malic 
acid ? Where is tannic acid found ? How is it prepared ? Give 
the process for making ink. What is leather? 




GALLIC ACID. 457 

characteristic precipitate it gives with iron, it is used 
as a test for that metal, which must, however, be in the 
state of peroxide, as the protosalts are unacted upon. 
The gradual darkening of pale writing inks is due to 
the slow oxidation of the iron they contain. Tannin is 
very valuable as a preservative in the dry collodion pro- 
cess ; a solution of it, being allowed to dry upon the sen- 
sitized collodion, will keep it in a condition impressible 
to light for many months. 

Tannigenic Acid — Catechine ( C 15 H 6 6 ) — is extract- 
ed by hot water from catechu. It forms white, silky 
crystals, not giving an insoluble precipitate with gela- 
tine, but producing a green color with persalts of iron. 
By the action of caustic potassa in excess it yields a 
black insoluble substance, Japonic Acid (C l2 H 4c 4: + 
HO). Carbonate of potassa converts it into a red acid, 
JRubinic Acid ( O lQ H 6 A ). 

In coffee and tea there exist similar acids, the Caffe- 
otannic (C u H 8 1 ) and Boheic (C u ITqOq). 

Gallic Acid ( C U JI 6 O 10 ) may be formed by exposing 
a solution of tannic acid to the air, or by making pow- 
dered galls into a paste with water, and keeping it ex- 
posed in a warm place to the air for some weeks. The 
mass is then pressed, and boiled with water. On cool- 
ing, the solution precipitates a quantity of gallic acid, 
which may be purified by recrystallization. Like tan- 
nic acid, this substance yields no precipitate with a pro- 
tosalt of iron, but a deep blue black with a persalt. It 
does not, however, precipitate gelatine; the crystals 
are soluble in one hundred parts of cold and three parts 
of boiling water ; the solution has an astringent taste. 
Gallic acid is used in photography for reducing silver 
from the nitrate and iodide of silver under the influence 
of light. 

Tannic acid passes into gallic acid by oxidation, car- 
bonic acid* and water being evolved. Dilute hydro- 
chloric or sulphuric acid convert it into gallic acid and 
sugar, 

C\,H 22 O u +10lTO=S(O u II, O 10 ) + C 12 H U O u ; 

What precipitate docs it yield with iron ? Of what use is it in 
photography? How does tannigenic acid originate? What acids 
exist in coffee and tea? How may gallic acid be prepared? Of 
what use is it ? When tannin oxidizes, what products arise ? 

u 



458 PYROGALLIC ACID. 

that is, one atom of tannic acid and ten of water pro- 
duce three of gallic acid and one of sugar. 

Ellagic Acid {C^H^+^HO) is produced with 
gallic acid when moistened galls are exposed to the air. 
It is a gray, crystalline powder, and has been found in 
the intestinal concretions called Oriental Bezoars. 

Pyrogallie Acid ( C 12 i^ 6 ) is largely manufactured 
for photographic uses, being one of the principal devel- 
opers in the collodion process. It is obtained by sub- 
liming gallic acid at a temperature between 410° and 
420° : pyrogallie and carbonic acids are produced, 

C u JI 6 O w =0 12 lI 6 6 +2C0 2 i 
that is, one atom of gallic acid yields one of pyrogallie 
and two of carbonic. It is in the form of white acicu- 
lar and lamellar crystals, feebly acid, and of an astrin- 
gent, bitter taste, soluble in water, alcohol, and ether. 
It is permanent when dry or dissolved in alcohol, but 
the aqueous solution oxidizes and turns brown. On ac- 
count of this property, it may be used for the analysis 
of air, especially when associated with an alkali. It 
gives a black precipitate with the salts of silver. 

Metagallic Acid (C^ 2 II±0^) is formed when gallic 
acid is suddenly heated in a retort to 500°. It is a 
black mass, insoluble in water, but soluble in alkalies, 
from which it is precipitated as a black powder by 
acids. 



LECTURE LXXXIV. 

The Vegetable Alkaloids. — General Properties of 
the Vegetable Alkaloids. — Morphia. — Narcotina. — 
Codeia. — Meeonic Acid. — Quinia. — Cinchonia. — 
Strychnia. — Brucia. — Artificial Alkaloids. — Ani- 
line, and the Dyes formed from it. 

The vegetable alkaloids constitute an extensive class 
of bodies, which are for the most part the active me- 
dicinal agents of the plants in which they occur. They 
are generally sparingly soluble in water, but more solu- 

What do Oriental Bezoars contain ? How is pyrogallie acid man- 
ufactured? What relation does it bear to gallic acid? What are 
its properties ? What is metagallic acid ? What general properties 
have the alkaloids ? 



MORPHIA. 459 

ble in boiling alcohol, of a bitter taste, and character- 
ized by containing nitrogen. In their natural state 
they are united with an acid, and, possessing basic prop- 
erties in a very marked manner, neutralize acids com- 
pletely. This quality seems to depend on the nitrogen 
they contain, and has no reference to their oxygen, for 
the quantity of this latter element present seems to have 
no relation to their neutralizing power, and, indeed, in 
some of them it is not present at all. In many respects 
they are analogous to ammonia, their salts, unlike those 
of some of the compound radicals, such as ethyle, un- 
dergoing decomposition in the same manner as the 
salts of ammonia. Thus the chloride of ethyle does not 
decompose the nitrate of silver, but the analogous com- 
pounds of ammonia and the vegetable alkaloids do ; and 
these bodies may therefore be separated from the natu- 
ral combinations in which they occur precisely as we 
should separate lime, or potassa, or magnesia in their 
salts. Most of the vegetable alkaloids are poisonous 
bodies, and, indeed, among them we meet with some of 
the most terrific poisons known. There are several ar- 
tificial substances, such as Aniline, and those containing 
arsenic and platinum, which ought to be classed with 
these basic bodies. 

One general method is applicable to the separation 
of these bodies. The substance containing them is 
boiled with dilute hydrochloric acid, the solution filter- 
ed, and treated with ammonia, lime, or magnesia. The 
alkaloid separates, and is purified by alcohol or ether. 
Most of these bodies are of importance in medicine. 

Morphia ( O 35 II 20 6 iV+ 2HO) is the active principle 
of opium, and was the first discovered of the alkaloids. 
It was isolated by Sertuerner in 1803. It may be pre- 
pared by mixing an infusion of opium with acetate of 
lead in excess ; the meconate of lead is separated by a 
filter, and through the solution containing acetate of 
morphia a stream of sulphureted hydrogen is passed. 
The solution is warmed to expel the excess of gas, fil- 
tered, and mixed with ammonia, w r hich throws down 
the morphia and narcotine : these are separated by boil- 

What relation have they to the animal system ? What is tly* gen- 
eral method for their separation ? What is morphia ? Give the pro- 
cess for making it. 



460 ALKALOIDS OF OPIUM. 

ing ether, which dissolves the latter. Turkey opium 
yields about an ounce to the pound of morphia. 

Morphia is, when obtained from its alcoholic solution, 
in small crystals, six-sided prisms with dihedral termin- 
ations. It is almost insoluble in water, bitter to the 
taste, neutralizes acids, and forms crystallizable salts. 
It dissolves readily in dilute acids ; the most common 
of its salts are the hydrochlorate, sulphate, and acetate. 
With nitric acid it gives a bright red color, with neu- 
tral perchloride of iron a blue color, and with iodic acid 
a reddish-brown color with the odor of iodine. 

JVarcotina (C 48 ZZ 24 15 iY r ) is associated with morphia 
in opium. It may be obtained by digesting powdered 
opium in warm ether, which takes up little else than the 
narcotina, and yields it in crystals — rhombic prisms in- 
soluble in cold water. It is soluble in volatile and fat 
oils, but insoluble in alkaline solutions : dilute acids form 
with it bitter solutions. By the action of peroxide of 
manganese and sulphuric acid, and by bichloride of pla- 
tinum, an extensive class of bodies is produced, some 
acids, others bases. 

Codeia (O 35 JI 20 O 5 ]^+2JIO) is found in the hydro- 
chlorate of morphia : it remains in solution when the 
morphia is precipitated by ammonia. It crystallizes in 
acicular or flat prisms, colorless and transparent. Nar- 
ceia, Thebaia, Papaverine, and Meconine are other crys- 
talline principles found in opium. 

Meconie Acid (C u ITO u +SirO), a tribasic acid as- 
sociated with morphia in opium. It may be obtained 
from the meconate of lime, which precipitates in the 
preparation of morphia by chloride of calcium from in- 
fusion of opium. The precipitate is washed in water 
and hot alcohol, and warm dilute hydrochloric acid is 
added until all the lime is removed. It crystallizes in 
transparent micaceous scales, soluble in water and alco- 
hol. When heated it loses 21^ per cent, of water, but 
if a strong solution be boiled it becomes dark-colored, 
carbonic acid is evolved, and oxalic acid and Comenic 
(Metameconic) acid are formed. The formula of co- 
menic acid is ((7 12 ^ 2 8 +2^ r O). Meconie acid forms 

What are its properties? How may narcotinc be obtained? 
Give the properties of codeia. What is the composition of meconie 
acid ? What bodies are derived from it ? 



QUININE. 461 

with the persalts of iron an intensely red color. It 
forms several series of salts, like all tribasic acids. 

Comenic acid, when heated, yields carbonic acid and 
Pyromeconic Acid (C l0 IT 3 O 5 + HO), with a small 
quantity of JParameconic Acid. 

Quinia — Quinine ((7 20 i7~ 12 iV^9 2 ). — This, which is one 
of the most valuable of the vegetable alkaloids, is ob- 
tained from Cinchona, Bark^ particularly predomina- 
ting in yellow bark. The decoction of the ground bark 
in dilute hydrochloric acid is to be boiled in an excess 
of milk of lime, and the precipitate acted upon by boil- 
ing alcohol ; on evaporation, Cinchonia is deposited in 
crystals, but the quinia remains in solution. It may be 
precipitated by the addition of water, and obtained in 
crystals from the spontaneous evaporation of its solu- 
tion in absolute alcohol. Quinia neutralizes acids per- 
fectly, giving rise to salts, of which the hydrochlorate, 
phosphate, sulphate, etc., are employed in medicine for 
the treatment of miasmatic disorders, and as tonics. It 
is sparingly soluble in water, but very soluble in alcohol 
or acids. The basic sulphate of quinine, a common 
preparation, is slightly soluble in water, the neutral sul- 
phate much more so. For this reason, sulphate of quinia 
is dissolved in dilute sulphuric acid ; the solution has a 
peculiar bluish opaline tint, the result of * fluorescence. 

Ginchonia {C^H^ON) is obtained, as just stated, 
in the preparation of quinia, with which it is associated 
in bark, and is found in the principal varieties of red 
and gray Peruvian bark. It crystallizes in prisms, re- 
quiring 2500 parts of water at 212° for their solution, 
and is sparingly soluble in alcohol, ether, and fixed oils. 
It has but little taste, but when mixed with an acid be- 
comes intensely bitter. 

Other analogous bodies exist in the different species 
of bark — Quinoidine, a mixture of quinine and Quini- 
dine (<7 4O iZ^i\^0 4 4-4J9r0), Quinicine (C^H^N^O^), 
and Aricine ( (7 48 ^ 6 iV^ 8 ) . 

Kinic Acid — Cinchonic Acid {C 1 B[ 5 5 +HO) — is 
combined with the foregoing bodies in bark. It is ob- 

Why is quinine valuable? What is its source? What salts are 
there of it ? What peculiarity has the solution of sulphate of qui- 
nine ? Describe cinchonia. What other bodies exist in bark ? How 
is kinic acid obtained ? 



462 



STRYCHNIA. — BRUCIA. 



tained by decomposing the kinate of lime, obtained in 
the manufacture of sulphate of quinine by oxalic acid, 
filtering the solution from oxalate of lime ; the kinic 
acid crystallizes on evaporation. It is very soluble in 
water. 

Strychnia ( O^H 24: O^N 2 ) occurs in Nux Vomica, St. 
Ignatius' s Bean, in the poison Upas Tieute, and other 
vegetable products. It may be extracted from nux 
vomica seeds by boiling them in dilute sulphuric acid, 
and then acting with lime and alcohol, as described in 
the case of quinia. 

Strychnia requires 7000 parts of cold and 2500 parts 
of boiling water to dissolve it ; water containing one 
forty-thousandth of its weight of it is rendered sensibly 
bitter. It forms a series of soluble, bitter, and poison- 
ous salts, and may be precipitated from their solutions 
by the caustic alkalies as a white substance, soluble in 
ether and chloroform. It is a violent poison, causing 
intense muscular contractions ; the antidote is tea. The 
best test is to immerse a frog partially in the suspected 
solution ; he will become tetanized if strychnia be pres- 
ent. 

Brucia {C^H 25 1 N 2 ) is associated with strychnia, 
and, being very soluble in cold alcohol, is readily sepa- 
rated from it. It is also more soluble in hot water, re- 
quiring only 500 parts. It has one sixth the poisoning 
power of strychnia. These substances are found in 
union with a peculiar acid, Strychnic or Igasuric Acid. 

The following table gives the names of other vegeta- 
ble alkaloids, and bodies analogous to them : 



Aconitine. 

Antearine. 

Asparagine. 

Atropine. 

Caffeine — Theine. 

Chelidonine. 

Colchicine. 

Conine. 

Curarine. 

Daphnine. 



Daturine. 

Delphinine. 

Elaterine. 

Emetine. 

Gentianine. 

Hesperidine. 

Hyosciamine. 

Meconine. 

Narceine. 

Nicotine. 



Picrotoxine. 

Piperine. 

Phloridzine. 

Populine. 

Salicine. 

Solanine. 

Stramonine. 

Thebaine. 

Theobromine. 

Veratrine. 



Nicotine is an oily liquid procured from tobacco ; iri- 

What is the source of strychnia ? What are its properties ? What 
effect has strychnia on animals ? Describe brucia. Name the veg- 
etable alkaloids. What are the properties of nicotine? 



ANILINE. 463 

flammable and poisonous, a single drop killing a dog. 
Conine, procured from hemlock, is a deadly poison, 
producing death by paralyzing the muscles of respira- 
tion. Two grains of it, neutralized with hydrochloric 
acid, and injected into the femoral vein of a dog, killed 
him in three seconds. Tlieine and Caffeine (C Q IT 5 2 
JYq) are found in coffee and tea. Their effect on the 
nervous system is well known. 

The following bases are formed artificially : 

Aniline — Kyanol ( C^H^N) — is one of the ingredi- 
ents of coal-tar. It may be obtained in large quantities 
by distilling nitrobenzole with a mixture of acetic acid 
and zinc or iron, in which case it is decomposed by nas- 
cent hydrogen. The decomposition is as follows : 

C 12 ff 5 ]^0,+Qll^ C l2 H,N+ 4,110; 
that is, one atom of nitrobenzole and six of hydrogen 
produce one atom of aniline and four of water. 

It is an oily liquid, boiling at 360°, specific gravity 
1.020 ; soluble in cold water, alcohol, ether, wood-spirit, 
•aldehyde, acetone, sulphide of carbon, and in fixed and 
volatile oils. It forms a series of salts with acids, and 
is now largely employed in the manufacture of the coal- 
tar colors. 

Aniline Purple {Mauve). — One equivalent of a neutral 
salt of aniline is dissolved in water, and boiled for sev- 
eral hours with six equivalents of chloride of copper. 
When the reaction is complete the mixture is filtered, 
the black precipitate well washed and dried, and after- 
ward digested repeatedly in dilute alcohol in order to 
dissolve out the coloring matter, which is aniline pur- 
ple. By heating anhydrous hydrochlorate of aniline 
with nitrate of lead to 360°, a bronze-like, brittle mass 
is obtained, which contains aniline red mixed with ani- 
line purple. The red may be separated from the pur- 
ple by boiling w r ater ; one grain of it will strongly color 
a gallon of water. These coloring matters are fixed on 
cotton by preparing the goods with a solution of tannin 
and the coloring matter, and then passing them through 
a bath containing tartar emetic. The tannate of anti- 
mony thus produced fixes the dye. 

What are the properties of coninc ? What is the composition of 
tlieine and caffeine. How is aniline made? What are the proper- 
ties of aniline ? Why is it valued ? 



464 THE ANILINE C0L0KS. 

Mauve is prepared by adding bichromate of potassa 
to sulphate of aniline : one tenth of a grain will form a 
rich violet-colored solution with a gallon of alcohol. 

Aniline Red {Magenta). — Corrosive sublimate and 
aniline form by mixture a colorless paste : when heated 
it acquires an intense crimson color. From this prod- 
uct, which seems to be a salt, Hosaniline ( C 2 qH 21 JST 3 0) 
is procured ; it acts the part of a base, and with acids, 
at a moderate heat, produces magenta. 

Hoseine results from the mixture of sulphate of ani- 
line and peroxide of lead. Fuchsirie is produced when 
aniline is heated with bichloride of tin, corrosive subli- 
mate, nitrate of mercury, arsenic acid, or indigo. Bleu 
de Paris arises when aniline is heated with bichloride 
of tin to a high temperature in a close vessel. 

The colors obtained by these processes depend on the 
oxidation of aniline, and vary with the degree of oxida- 
tion. The processes of Perkins, in which the oxidation 
is effected by bichromate of potassa, produce very per- 
fect colors. Variation of tint depends on the propor-" 
tion of the ingredients used ; for example, 10 parts of 
aniline added to a mixture of 12 of arsenic acid and 12 
of water, and heated to about 248°, yield a rich red with 
a violet tint. The same quantity of aniline, with 24 of 
arsenic acid and 24 of water, give a purple or violet. 

The selection of a proper mordant materially affects 
the results. Of all yet proposed, the stannate of soda 
appears to be the most efficient. 

Leukol (C lQ IT 8 ]Sr)) formed with aniline in oil of coal- 
tar, from which it may be separated by distillation. It 
is also an oily liquid, and can yield crystallizable salts. 

Quinoline (C 19 Hq]¥), made by distilling quinine or 
strychnine with caustic potassa. An oily liquid, very 
bitter, strongly alkaline, yielding crystallizable salts. 

Besides these bodies, there are other artificial bases 
of an analogous nature, but which differ in the remark- 
able particular of containing platinum and arsenic; such, 
for example, as the platinum bases of Reiset and Gros, or 

How is mauve produced ? What mordant does it require? How 
is magenta made ? How are roseine, fuchsine, and bleu de Paris 
prepared ? What is the chemical explanation of the aniline colors ? 
What is the best mordant for them? How is quinoline made? 
What other organic bases are there ? 



COLORING BODIES. 465 

the arsenico-platinum radical kakoplatyle. The forma- 
tion of these organic bases leads us to hope that the 
vegetable alkaloids themselves will hereafter be artifi- 
cially formed. 



LECTURE LXXXV. 

The Coloring- Bodies. — Their General Properties, — 
Dyeing. — The Non-nitrogenized Coloring Matters. — 
The Nitrogenized Coloring Matters. — Indigo. — Col- 
orless Indigo. — Bodies derived from Indigo. — Lit- 
mus. — Chlorophyll. — Carmine. 

The coloring principles derived from the organic 
kingdom may be conveniently divided into two classes, 
the non-nitrogenized and the nitrogenized. They may 
also be readily classed into groups, as blue, red, yellow, 
green. For the most part they are derived from vege- 
table productions. 

For some coloring matters, the fibres of those tissues 
commonly employed for clothing have a sufficient affini- 
ty to hold the color so that it can not be removed by 
mere washing, and is permanently dyed. Such colors 
are called substantive. But in other instances this is 
not the case ; the artist has then to avail himself of the 
properties possessed by intermediate bodies, such as 
alumina and the oxide of tin, called mordants, which at 
once possess the double quality of an affinity for the col- 
oring matter and an affinity for the cloth fibre. Colors 
requiring a mordant are termed adjective colors. The 
attraction of these bodies for coloring matter may be 
illustrated by precipitating alumina in a solution tinged 
by litmus ; the solution becomes perfectly clear, its color 
going down with the precipitate, and forming with it a 
lake. 

Non-nitrogenized Coloring Matters. 

The blue non-nitrogenized coloring. matters are chiefly 
found in flowers and fruits. They are reddened by acids, 
and turned green by alkalies. 

The red non-nitrogenized coloring matters are of some 

What division is made of coloring principles? What is a sub- 
stantive color? What is a mordant? What is an adjective color? 

TJ2 



466 COLORING MATTERS. 

importance ; among them may be mentioned Madder or 
Garancine. The plant is largely cultivated in Holland, 
and has a long, spreading root, which develops a red 
color during dyeing. Alizarine ( C 20 TIq 6 ) is obtained 
by digesting garancine in boiling alcohol. Madder Lake 
is made by adding carbonate of soda to a decoction of 
madder root in alum. 

Hmmatoxyline (C^JE^ 6 +HO) is the coloring mat- 
ter of logwood. It is soluble in water and alcohol, and 
furnishes, with iron and alum bases, a black dye. The 
same principle is yielded by Brazil-wood and camwood. 

Carthamine is a very beautiful red, obtained from the 
safflower. It is used in making pink saucers, and in the 
preparation of Rouge. 

The yellow coloring matters. Among these may be 
mentioned Quercitrine (C 32 lfi 5 14 ), derived from the 
Quercus Tinctoria; Gamboge, the dried juice of the 
Garcinia Gambogia ; Turmeric, used as a test for alka- 
lies, which turn it brown, from the Curcuma Longa; 
and Anatto, employed for coloring cheese, from the 
seeds of Bixa Orellana. 

NlTROGENIZED COLORING MATTERS. 

The nitrogenized coloring matters, among which are 
some of the most valuable dyes that we possess, may be 
divided according to their tint. 

Indigo is derived from the juice of several species of 
Indigofera, and is formed from a colorless or yellow 
compound, which is dissolved out from the leaves of 
these plants when they are allowed to ferment with wa- 
ter. A deep blue precipitate forms on the addition of 
lime-water and exposure to the air. It appears, there- 
fore, to be a product of oxidation. It comes, in com- 
merce, in small masses of a conchoid al fracture, which, 
when rubbed, exhibit a coppery aspect ; is insoluble in 
water, alcohol, dilute acids, and alkalies ; and may be 
sublimed, yielding a purple vapor, which condenses into 
crystals of pure indigo. It dissolves in about 15 parts 
of strong sulphuric acid, but still better in N"ordhausen 
oil of vitriol. The mass produced is soluble in water ; 

What is madder? What are the reactions of hsematoxyline ? 
What is rouge ? Name some of the yellow coloring matters. What 
is the source of indigo ? What are its properties ? 



INDIGO. 467 

it is a solution of Sulphindigotic Acid ( (7 16 j5^ 2 jST+ 

8 2 S +H0). 

By contact with deoxidizing agents blue indigo be- 
comes colorless, as may be shown by digesting powder- 
ed indigo, protosulphate of iron, hydrate of lime, and 
water together. In this state, as in its natural condi- 
tion, it is soluble in water, and may be precipitated by 
hydrochloric acid. On exposure to the air, Bidigogene, 
as this white indigo is called, absorbs oxygen rapidly, 
and becomes blue and insoluble. 

When indigo is submitted to destructive distillation, 
it yields aniline, described in the last Lecture. 

The relation existing between blue and white indigo 
is seen from their formulas : 

Blue Indigo — Indigotine C 16 H 5 N0 2 

White Indigo — Indigogene C 16 H 6 N0 2 . 

Under the action of heat and of reagents indigo yields 
an extensive class of bodies, to which much attention 
has been given. With dilute nitric acid it yields Anilic 
or Indigotic Acid ; with strong nitric acid, Picric or 
Carbazotic Acid (C 12 IT 2 (]Sr0 4 ) 3 O^IlO) i a substance of 
a yellow color, bitter taste, and forming explosive salts. 
Heated with bichromate of potassa, sulphuric acid, and 
water, it yields Isatine {C^^O^JST)^ which crystallizes 
in reddish-brown prismatic crystals, inodorous, sparing- 
ly soluble in cold, but more so in hot water, readily sol- 
uble in alcohol, but less abundantly in ether. This body, 
under the influence of an alkaline solution, unites with 
one atom of water and changes into Isatinic Acid. 
Under the influence of chlorine, isatine yields Chlorisa- 
tine 9 an atom of chlorine substituting one of its hydro- 
gen atoms ; and Bichlorisatine by the substitution of 
two chlorine atoms for two hydrogen ones; and these 
again, as in the cuse of isatine itself, acted upon by al- 
kaline solutions, yield each an acid. With bromine it 
produces Bromisatine and Bibromisatine. Caustic al- 
kalies acting on indigo yield Chrysanilic and Anthra- 
nilic Acids. 

Litmus is derived from the Rocella Tinctoria, Lecano- 

How is indigogene prepared ? What is the relation between blue 
and white indigo ? How are indigotic and picric acids made ? De- 
scribe isatine. What bodies arise from isatine ? What is the source 
of litmus ? 



468 LITMUS. — CHLOROPHYLL. 

ra Tartaria, etc. These lichens give up to ether a crys- 
talline substance, to which the name of JLecanorine is 
given. Its composition is ( C 1q Sq O q +ITO) ; it does not 
contain nitrogen. It is in white, inodorous, and taste- 
less stellated groups of acicular crystals, soluble in alco- 
hol and ether. This substance, heated with baryta or 
alkalies, produces Orcine (C 16 H Q 4 +ITO) by losing 
two atoms of carbonic acid. Orcine crystallizes in flat, 
four-sided prisms, with dihedral summits : it has a sweet, 
repulsive taste, is vaporizable at 550°. Mixed with am- 
monia and exposed to the air, oxygen is absorbed, and 
the liquid assumes a deep purple tint. From this, acetic 
acid precipitates a deep red powder, Orceine or Orceic 
Acid ( C 16 IT 9 7 iV), which contains nitrogen, and is sup- 
posed to be the basis of the dye-stuff of litmus : with al- 
kalies it gives a blue color. Litmus is extensively used 
in chemistry as a test for acids and alkalies. Litmus 
paper is white unsized paper, stained with an infusion 
of an ounce of litmus in half a pint of boiling water. 

Chlorophyll ( C 18 IT Q 8 N) is the green coloring mat- 
ter of leaves. It is insoluble in water, but soluble in 
water and ether, and is a fatty substance. It is also 
found, under very interesting circumstances, in the ani- 
mal system, as the coloring matter of bile. When an 
ethereal solution of it is long exposed to light, it ac- 
quires a yellow color, and leaves, on evaporation, a resi- 
due having all the characters of xanthophylline. 

Xanthophylline is a term applied to the coloring 
matter extracted from the yellow leaves of autumn. 
JErythrophyUine is obtained by digesting the leaves 
which redden, in alcohol. 

Carmine is the coloring matter of the cochineal in- 
sect, Coccus Cacti. The coloring matter may be ob- 
tained from the insect by water or ammonia. The car- 
mine of commerce is a lake prepared by adding alum to 
the freshly-filtered solution. 

Aloes is the inspissated juice of certain species of 
Aloe, used as a purgative medicine. When heated 
with nitric acid, and water added, a yellow precipitate 
is thrown down, which, when purified, is Chrysammic 

How are orcine and orceine made ? What is chlorophyll ? What 
substances are made from autumn leaves ? What is carmine ? Of 
what use is aloes ? What is chrysammic acid ? 



THE FATTY BODIES. 469 

Acid, It yields yellow crystals of a bitter taste, and 
furnishes a solution of a purple color. Its salts are 
crystallizable, by transmitted light of a red color, with 
a green metallic reflection, like murexide. The liquid 
from which this acid was precipitated contains picric 
acid. 



LECTURE LXXXVL 

The Fatty Bodies. — Characteristics of the Fatty Bod- 
ies. — Fats. — Fixed and Volatile Oils. — Soaps. — Ste- 
arine and Stearic Acid. — Margarine and Margaric 
Acid. — Oleine. — Glycerine. — The Natural Oils, 
Palm Oil, etc. — The Volatile Oils. — The Camphors. 

This class of bodies is characterized by several well- 
marked peculiarities, and may be conveniently divided 
into two natural groups, oils and fats. They belong 
both to the vegetable and animal systems. In the for- 
mer they usually abound in the seeds or fruits ; in the 
latter, are deposited in the cellular structure of the adi- 
pose tissue. The natural fats are usually mixtures of 
two or more ingredients, differing from one another in 
consistency. In most instances they are stearine and 
margarine, along with a liquid, oleine. These oils can 
not be distilled without undergoing decomposition ; ex- 
posed to the air they gradually absorb oxygen and 
evolve carbonic acid. Many of them, in which this 
change takes place with rapidity, turn into resinous bod- 
ies, and hence their application in painting as drying 
oils. Linseed oil, which is the most used for such pur- 
poses, has its drying qualities increased by boiling with 
litharge, and is also an important component of Printers'' 
Ink, for which it is first heated and then set on fire, 
and allowed to burn for some time. When extinguish- 
ed it is miscible with fresh oil or turpentine, and about 
a sixth of lamp-black is added. 

Oily bodies may be divided into fixed and volatile ; 
the former decompose when heated, the latter distill. 

What are the general properties of the fatty bodies ? What in- 
gredients are there in natural fats ? What change do the oils suffer 
in the air? Why is linseed oil valuable? How is printers' ink 
made ? What division is made of oils ? 



470 PROPERTIES OF OILS. 

A simple test suffices to distinguish them. When a few 
drops of an oily substance are put on paper, if it be a 
volatile oil it soon evaporates, and leaves the paper 
without a stain ; if fixed, the paper remains greasy. 
The fixed oils have but little odor, the volatile oils com- 
monly a characteristic one. They are all insoluble in 
water ; many are soluble in alcohol ; all are dissolved 
by ether. 

By exposure to a low temperature the constituent 
principles of a mixed oil may often be separated from 
each other, the more solid substances separating first. 
When olive oil is thus treated, an exposure to 40° 
causes a deposit of Margarine y the fluid portion which 
is left is Oleine. Animal fats exposed to pressure be- 
tween folds of blotting-paper communicate to it oleine, 
and the solid residue left behind is a mixture of marga- 
rine and Stearine. When the fixed fats are boiled with 
alkaline solutions, Soaps are formed. These substances, 
of extensive use in domestic economy and the arts from 
their detergent properties, are freely soluble in wa- 
ter. In the process of making them the fats undergo a 
change, true acids being liberated, which unite with the 
alkaline base. Stearine yields stearic acid ; margarine, 
margaric acid ; and oleine, oleic acid. They may be set 
free by decomposing the soap with an acid. At the 
same time, a sweet substance, Glycerine^ appears ; it is 
the base with which the acids were associated, oleine 
being, for instance, an oleate of glycerine. Of the vari- 
eties of soap met with in commerce, Soft Soap is made 
from potassa, combined with whale or seal oil; Hard 
White Soap from tallow and caustic soda ; Sard Yel- 
low Soap from soda, tallow, palm-oil, and resin. In the 
preparation of white soap the alkaline solution is made 
to boil, and tallow added in small portions until no 
more can be saponified. The solution now contains 
soap and free glycerine ; the former is separated by the 
addition of common salt in a solution of which it is in- 
soluble. It floats on the top of the liquid, and is then 
run into moulds, and cut into bars for commerce. In 

How are oils distinguished? What is the process for analyzing 
mixed oils ? What is soap ? What is the reason of the appearance 
of glycerine ? What is the difference between soft and hard soap ? 
Describe the manufacture of soap. 



STEAEINE. — MAKGAHINE. — OLEINE. 471 

this process the manufacturer does not add so much 
salt as to separate all the water. Commercial soap still 
contains from forty to fifty per cent. 

Stearine ( C lu IT no O l2 ) may be obtained from purified 
mutton fat by suffering a warm ethereal solution to cool. 
The stearine crystallizes, and margarine and oleine are 
left in solution. A repetition of the process purifies it. 
It is a w T hite body, insoluble in water and cold alcohol, 
fusing at 140°; when saponified it yields glycerine and 
stearic acid. 

Stearic Acid (C 3 qH 35 3 +H0) may be obtained by 
decomposing a soluble stearine soap by tartaric acid, 
and purifying the product by solution in boiling alco- 
hol, from which it separates in crystalline flakes. It is 
white, inodorous, and tasteless; fuses at 160°, reddens 
litmus, may be distilled in vacuo, but is decomposed by 
a high heat in the open air. It forms monobasic and 
bibasic salts. 

Margarine ( C 10Q JT 104: 12 ) is best obtained from olive 
oil by cooling it to 32°, pressing out the oleine, and dis- 
solving the residue in boiling alcohol, from which the 
margarine separates in pearly crystals. 

Margaric Acid (C u il 33 3 +JIO) is obtained by de- 
composing the soap of olive-oil and potassa by acetate 
of lead or chloride of calcium. The oleate and marga- 
rate of lead or lime is formed, the oleate is extracted 
by cold ether, and the remaining margarate decomposed 
by dilute hydrochloric or nitric acid. It crystallizes in 
white needles, the melting point being 140°. 

Oleine (C lu IT 10 ±O 12 ). — When almond or rape oil is 
dissolved in ether, and the solution exposed to a low 
temperature, the margarine crystallizes, and oleine may 
be obtained by evaporating the ether. It remains liq- 
uid at a temperature of 0°. 

Oleic Acid (0 36 IT 33 3 ) is obtained from oleine by sa- 
ponification and decomposition with hydrochloric acid, 
as in the foregoing instances. It solidifies at about 50°, 
and gives rise to a series of salts. 

3fargarone (0 6G IT 6 q0 2 ). — When a mixture of mar- 
garic acid and lime is distilled this substance is formed, 

How may stearine and stearic acid be obtained? How may mar- 
garine and margaric acid be obtained? Describe the preparation 
of oleine and oleic acid. What is margarone? 



472 GLYCERINE. — PALM OIL. — FATS. 

and carbonic acid separates. It is a white solid, like 
spermaceti, and melts at 170°. 

Glycerine (C 6 ITq0 6 ) arises when any fatty matter is 
saponified with potassa, the soap being decomposed by 
tartaric acid and the glycerine dissolved out by alcohol. 
It is a sweet, colorless liquid, specific gravity 1.28, sol- 
uble in water and alcohol, but not in ether. It is not 
susceptible of vinous fermentation, but when left for 
some months in a warm place it produces Propionic 
Acid. Mixed with sulphuric acid, the two bodies unite, 
and Sulphogly eerie Acid (C 8 IT 5 1 + 2S0 3 ) is the re- 
sult, an acid having many analogies with sulphovinic. A 
corresponding Phosphogly eerie Acid is said to exist in 
the brain and yolk of egg. When glycerine is dropped 
into equal parts of strong nitric and sulphuric acids, 
Nitroglycerine (C 6 ir 6 (NO±) 2 6 ), a very explosive and 
poisonous body, is formed. 

Palm Oifis brought from Africa, and is used in the 
manufacture of yellow soap. It is of a reddish-yellow 
color, and contains, besides oleine, a solid fat, Palmitine. 
It is insoluble in water, slightly soluble in hot alcohol, 
but very soluble in ether. Its melting point is 118°. 
By saponification and decomposition with an acid it 
yields Palmitic Acid, the melting point of which is 
140°. It is a bibasic acid. 

Cocoa Tallow. — A solid fat obtained from the cocoa- 
nut, and used in the manufacture of candles. Its oleine 
and stearine may be separated by pressure or by boil- 
ing alcohol, from which the stearine crystallizes on 
cooling. 

Among other fatty substances and allied bodies may 
be mentioned Nutmeg Butter, which yields, among 
other products, Myristicine, and, by saponification, My- 
ristic Acid. Elaidine arises from the action of nitrous 
acid on oleine ; it furnishes, by the common process, 
Elaidic Acid. Suberic Acid arises from the action of 
nitric acid on cork; Succinic Acid, by the destructive 
distillation of amber, or by the continued action of ni- 
tric on stearic acid ; Sebacic Acid, by the destructive 
distillation of oleic acid. Putyrine, Oaproine, and Ca- 

When does glycerine arise? What bodies arise from glycerine? 
Describe palm oil. What is cocoa tallow ? Name some other fatty 
substances and allied bodies. 



THE VOLATILE OILS. 4*73 

prine, which are contained in butter, yield, by saponifi- 
cation and decomposition, Butyric, Caproic, and Capric 
Acids. Butyric acid can be made, as we have seen, art- 
ificially by fermentation. Bees' Wax is a mixture of 
three bodies — Myricine, insoluble in alcohol ; Cerine, de- 
posited in crystals as the solution cools ; and Ceroleine, 
which is retained in solution. Vegetable wax is yield- 
ed by the Myrica Cerifera and some other trees. Sper- 
maceti is obtained from certain species of whales; 
it yields, under the process for glycerine, a substance, 
Ethal ; and this, under the action of hot potassa, gives 
Ethalic Acid, with evolution of hydrogen gas. Choles- 
terine is obtained from biliary calculi ; it also occurs in 
the substance of the brain. 

The Volatile Oils. — These, for the most part, are 
found in plants, or are derived from them by simple pro- 
cesses. Many of -them are extensively used iri the arts 
in the manufacture of varnishes, and others in the prep- 
aration of perfumery. Their solutions in alcohol form 
Essences, and in water Medicated Waters. They are 
commonly obtained by the distillation of those parts of 
the plants in which they occur with water, and consist 
of two substances — a solid portion, or Stearopte?ie, or 
camphor, and an Elaioptene, or true oil. The former is 
an oxyhydrocarbon, the latter a hydrocarbon. The vol- 
atile oils may be divided into groups according to their 
constitution. 

Volatile Oils containing Carbon and Hydrogen 



Turpentine. 


Bergamotte. 


Citron. 


Cubebs. 


Copaiva. 


Etc. 


Storax. 




• Volatile Oils containing Carbon, Hydrogen, Oxygen. 


Cajeptit. 


Pennyroyal. 


Lavender. 


Valerian. 


Rosemary. 


Spearmint. 


Peppermint. 


Etc. 


Volatile Oils containing Sidphxtr. 


Black Mustard. Onions. 


Horseradish. Asafcetida. 



What is bees' wax ? What is spermaceti ? Of what use are the 
volatile oils? What are essences and medicated waters? What is 
meant by stearoptene and elaioptene ? What are the groups of vol- 
atile oils ? 



474 STEAROPTENS. 

Of the first group, Oil of Turpentine may be taken as 
the type ; the elementary composition may be regarded 
as ( C 5 H±). It is principally procured from North Caro- 
lina, and is resolved by distillation into the volatile oil 
and Yellow Mosin. Artificial Camphor is made by pass- 
ing dry hydrochloric acid gas into oil of turpentine : its 
constitution is (C 20 D r 16 -{-JICl). 

The stearoptens or camphors originate in several dif- 
ferent ways ; sometimes by the oxidation of the oils 
from which they are derived, sometimes they are hy- 
drates of these oils, and sometimes they are isomeric 
with them. The stearoptens are best represented by 
common camphor, which is extracted from the Laurus 
Camphor a of Japan, China, and Java by distillation 
with water. It is a white, tough, and semi-transparent 
mass ; specific gravity .990 ; fuses at 370°, boils at 400°, 
and maybe distilled without decomposition. It vapor- 
izes at common temperatures, and its motion toward the 
light has been made the subject of interesting research- 
es by Professor J. W. Draper. 

Of the oils containing sulphur, the oil of black mustard 
seed ( CJS^SFS^) is a good example : it arises from the ac- 
tion ofmyrosine upon sinapine in the presence of water. 
It has been regarded as the sulphocyanide of AUyl (C G 
H 5 ). Oil of Garlic is an oxide and sulphide of ally]. 



LECTURE LXXXVII. 

The Resins, Balsams, and Bodies arising in De- 
structive Distillation. — Posin. — Shellac. — Am- 
ber. — Caoutchouc. — Yitlcanization. — Gutta Percha. 
— Products of the Destructive Distillation of Wood. 
— Tar. — Pitch. — Paraffine. — Creosote. —Destructive 
Distillation of Coed. — Coal Oil. — Carbolic Acid. — 
Products of Slow Decay. — The Varieties of Coal. — 
Petroleum, 

The resins are bodies in many respects analogous to 
the camphors, but are distinguished from them by the 

What is the composition of oil of turpentine ? How do the cam- 
phors originate? Describe common camphor. -What singular rela- 
tion has it to light? What is the composition of oil of mustard? 
What are the resins ? 



THE RESINS. 475 

circumstance that they are not volatile without decom- 
position. In many instances they act as acids ; they all 
contain oxygen. 

Colophony {Common Rosin) is a mixed resin, ob- 
tained by the distillation of turpentine with water, the 
oil of turpentine passing over. It is a mixture of two 
resins, Pinic and Silvio Acids, which may be separated 
by cold alcohol, in which the latter is insoluble. 

Gum Lao, which is one of the resins, occurs under 
three forms — shell lac, stick lac, and seed lac. It is used 
in the preparation of lacquers, and is the chief ingredient 
in sealing-wax. Among other resins may be mentioned 
Copal, Mastic, Dragons'* Blood, Gamboge, Sandarac, 
and Dammar. 

Amber is a substance belonging to this class. It is 
found in beds of bituminous wood, and often incloses in- 
sects in a state of beautiful preservation. Its specific 
gravity is about 1.07. By distillation it yields succinic 
acid. 

Caoutchouc — India Rubber — Gum Elastic — is the 
produce of the Jatropha Elastica, the Urceola Elastica, 
and several other tropical trees. It is found in small 
proportion in the poppy, lettuce, euphorbium, and other 
plants having a viscid, milky sap. The fresh juice is a 
yellow, milky fluid, which, when exposed to warm air, 
forms an elastic deposit of a dark color. Caoutchouc is 
a hydrocarbon, having the composition C Q H 7 . 

In its ordinary state it hardens at low temperatures, 
but does not become brittle; melts at 250°, and does 
not regain its former state on cooling. It is softened 
and dissolved by ether, chloroform, bisulphide of car- 
bon, oil of turpentine, and coal naphtha. By the process 
of vulcanization, in which it is subjected to the action 
of sulphur at a temperature of about 300°, it is so modi- 
fied that it resists the action of its ordinary solvents, and 
retains its pliability at both low and high temperatures. 
A hard compound of sulphur and rubber is called Ebon- 
ite. A large quantity of silicate of magnesia in fine pow- 
der is sometimes incorporated with the rubber before 

How is common rosin obtained ? What are the forms of gum lac? 
What is amber? What is the source of caoutchouc? What arc its 
properties? Describe the process of vulcanization. Of what use is 
the silicate of magnesia in vulcanization ? 



476 PRODUCTS OF DESTRUCTIVE DISTILLATION. 

vulcanization, to give a smooth and non-adherent sur- 
face. Marine Glue is made by dissolving a mixture of 
caoutchouc and shell lac in coal naphtha. 

Gutta Percha is closely allied to caoutchouc, and is 
produced by the Isonandra Percha, a tree abounding in 
the islands of the Eastern Archipelago. It is a tough, 
unyielding, fibrous substance, of a black or brown color. 
When softened in hot water it admits of being mould- 
ed, and hardens again on cooling. It is an excellent in- 
sulator for submarine cables, and is applied to many 
purposes in the arts. 

Gum Resins are natural mixtures of gum and resin, 
and often include volatile oils. 

Balsams are compounds of resins with volatile oils : 
some of them also contain benzoic or cinnamic acid. 
Some, as benzoin, are solid ; others, as Balsam of Toht 
and Peru, and Canada Balsam, are viscid fluids. 

The Products of the Destructive Distillation of 
Wood, etc. 

When wood is submitted to distillation in close ves- 
sels, a thick, black, inflammable liquid, Tar, is formed. 
It contains a great many remarkable bodies, among 
which the following may be mentioned. The solid 
black residue which is left after the distillation or in- 
spissation of tar is Pitch. 

Paraffine ( CH) was originally discovered among the 
products of distillation of wood-tar, but is more abund- 
antly obtained from the distillation of bituminous schists 
and petroleums. It is a crystalline solid, without taste 
or odor. Its specific gravity is .87, melts at 112°, and 
distills unchanged. Few chemical agents act upon it ; 
it remains unchanged by the acids, alkalies, etc., but is 
soluble in turpentine and naphtha. From its chemical 
indifference it has obtained its name (Parum Affinis). 
It is used in the manufacture of candles, and as a sub- 
stitute for wax. 

Eupion (C 5 IT 6 ) occurs abundantly in animal tar, 
from which it may be prepared by distillation, and sub- 
Whence does gutta percha come ? How may it be moulded ? 
What are balsams? What products arise from the destructive dis- 
tillation of wood ? What is paraffine ? What are its properties ? 
Why is it so called ? How is eupion prepared ? 



CREASOTE. — NAPHTHALINE. 477 

sequently purified by rectification from sulphuric acid. 
From paraffine it may be separated by exposure to cold, 
or, being more volatile, by distillation. It is a colorless 
liquid, specific gravity .074, boils at 339°, insoluble in 
water, but very soluble in alcohol. 

Creosote (C l6 IT l0 O 2 ) is extracted from the heavy oil 
of tar by a complicated process. It is an oily, colorless 
liquid, of burning taste, exhaling an odor of wood- 
smoke ; specific gravity 1.04 ; boils at 400 ; burns with a 
sooty flame ; is sparingly soluble in water, but very sol- 
uble in alcohol, ether, benzole, and acetic acid. It has 
the remarkable property of coagulating albumen and 
preserving flesh from putrefactive changes, whence its 
name. It is useful in toothache. 

Among the allied substances maybe mentioned JPica- 
mar, an oily liquid, of a bitter taste, which boils at 518°, 
and combines with bases to form crystalline compounds. 
Kapnomar, a colorless liquid, having an odor of rum ; 
boils at 360°, and forms with oil of vitriol a purple so- 
lution. Cedriret, which forms red crystals, giving with 
creasote a purple solution, and with sulphuric acid a 
blue. Pittakal) a dark blue solid, yields blue precipi- 
tates with metallic salts, and contains nitrogen. 

When coal-tar is submitted to distillation, like wood- 
tar it yields a volatile oil, which, by being submitted to 
rectification, becomes Coal Oil, or Artificial Naphtha. 
From it a variety of substances maybe extracted; they 
either pre-exist in the oil, or are formed by the opera- 
tion. 

Naphthaline (C 20 ITq), obtained by distillation of 
coal-tar, is a white, crystalline substance ; melts at 176°, 
boils at 420°, specific gravity 1.05, exhales an odor like 
the narcissus, is combustible, insoluble in water, solu- 
ble in ether and alcohol. It dissolves in sulphuric acid, 
and the solution, on being diluted with water and satu- 
rated with carbonate of baryta, yields a salt containing 
Sulphonaphthalic Acid ((7 20 ^#2#5+-#XO. 

Paranaphthaline ((7 30 ^T 12 ) is associated with naph- 
thaline, but differs from it in being insoluble in alcohol, 
by which liquid they may therefore be separated. 

What are the properties of creasote? Describe some of the allied 
substances. How is coal oil produced ? Describe naphthaline. 
How does paranaphthaline differ from it? 



478 DECOMPOSITION OF WOODY MATTEK. 

Carbolic Acid — Phenylic Acid {0^11^0+ HO) — is 
found in that portion of oil of tar which boils between 
300° and 400°. This, being agitated with potassa, and 
the result decomposed by an acid, yields carbolic acid, 
which may be purified by rectification from caustic po- 
tassa. The pure acid forms a colorless, deliquescent, 
crystalline mass, fusing at 95°, and passing into vapor at 
370°. It has a smoky odor, an acrid taste, and the an- 
tiseptic properties of creasote. It is much used- as a 
disinfectant, and has a singular power in increasing 
friction ; it is useful in boring glass. 

When woody matter is gradually decomposed by con- 
tact with air and moisture, Geine^ UumiCs, and Ulmine 
are produced. They arise from a partial oxidation, at- 
tended by the production of carbonic acid and water, 
the actipn being originally occasioned by nitrogenized 
matter in the wood. Corrosive sublimate, or any other 
body possessing the power of checking ferment action, 
may therefore be resorted to for preventing the dry rot 
of wood. These brown bodies, which are found in soils 
and moulds, combine with alkalies, and have been de- 
scribed as Gfeic, Humic, and Ulmic Acids. When the 
access of air is for the most part cut off, ulmine, etc., do 
not appear alone, but with them many other substances 
of the family of the hydrocarbons arise. Besides these, 
in the formation of vegetable soil and turf, azotized 
acids, such as Crenic and Apocvenic, appear. These 
originate in the decay of the nitrogenized constituents 
of the wood, an action which probably precedes its gen- 
eral disorganization. They are often found in mineral 
springs in combination with oxide of iron, forming 
ochery stains. 

There is abundant proof that all the varieties of coal 
have originated from woody fibre. For the production 
of these it seems necessary that the wood should be im- 
mersed in water at a moderately high temperature, and 
without free contact of air. The ulmine bodies form 
from the decay of wood at the surface of the earth ; the 
coal bodies under a heavy pressure. Of them we have 

How is carbolic acid made? What are its properties? Why is 
it useful for boring glass? When do geine, humus, and ulmine 
arise? How may woody matter be preserved ? What other bodies 
do soil and turf contain ? What is the origin of coal ? 



BITUMEN. ASPH ALTUM. — PETROLEUM. 479 

many varieties, differing much in constitution. Lignite 
is of a brown color, and in it the structure of the wood 
is more or less perfectly preserved ; the various forms 
of Bituminous Coal, as cannel coal, etc. ; Anthracite^ 
which contains but little hydrogen. 

The essential elements of coal are carbon and hydro- 
gen, but it also contains oxygen, nitrogen, sulphur, and 
various mineral matters, constituting the incombustible 
ash, chiefly silicious matter and unburnt carbon, with 
carbonate of lime and oxide of iron. 

Bitumen, Asphaltum, Petroleum, are substances 
closely allied to coal. Many kinds of coal may be re- 
garded as carbonaceous matter impregnated with bitu- 
men, and Bituminous Schists are earthy compounds 
similarly impregnated. 

Asphaltum may be taken as the type of the bitumens. 
It occurs on the shores of the Dead Sea, in Trinidad, and 
many other places. It has a dark brown or black color, 
resinous fracture, burns with a smoky flame, is soluble 
in alcohol, ether, and benzole. Mixed with lime, chalk, 
sand, etc., it is used for pavements and water-proof ce- 
ments. 

Petroleum, a fluid substance found in America and 
the Burmese Empire to an enormous extent, and used 
as a fuel and for illumination, arises probably from the 
distillation of bituminous coal and shales by the internal 
heat of the earth. The annual production of the Ran- 
goon wells in Burmah is 400,000 hogsheads ; 80,000,000 
of gallons were thrown out by the wells in the United 
States in 1863. It is also found in many other localities. 

The wells in the United States are sunk from 100 to 
450 feet through the sandstones of ^he Devonian series, 
or the coal measures which overlie these strata. In 
Canada the oil is found in shales and limestones. The 
quantity thrown out by some of these wells in a day has 
exceeded 2000 barrels of forty gallons. In many the 
aid of steam-pumps is required. 

Petroleum may be regarded as a compound of various 

What are the varieties of coal ? What is the composition of coal ? 
What substances are allied to coal? Where is asphaltum found? 
Where does petroleum occur most extensively ? What is the annual 
production ? In what formation is the oil found ? What is the com- 
position of petroleum ? 



480 ANIMAL CHEMISTRY. 

hydrocarbons boiling at different temperatures. When 
subjected to fractional distillation it yields Benzine, used 
by painters as a substitute for turpentine ; Kerosene, em- 
ployed for illuminating purposes ; Lubricating Oils of 
greater specific gravity, and Paraffine. 



LECTURE LXXXVIII. 

Animal Chemistry. — The Animal System changes 
incessantly. — Chemical Processes interior to it — Ob- 
jects of Digestion. — Description of the Process. — Va- 
rieties of Food. — Absorption into the System by Dac- 
teals and Veins. 

In the preceding Lectures I have given the descrip- 
tive history of many of the more important organic 
compounds, and chiefly those belonging to or derived 
from the vegetable kingdom. It remains now to men- 
tion another class, which seems to bear a closer relation 
to animal beings. The appearance and destruction of 
these compounds lead by ready steps to the considera- 
tion of the physiological functions of the animal mech- 
anism. 

There are certain causes which tend constantly to 
change the weight of an adult, healthy individual — 
causes of increase and causes of diminution. Among 
the former may be mentioned food, drink, and atmos- 
pheric air; among the latter, urine, feces, transpired 
and expired matters ; and these, in the course of a year, 
amount to many hundred pounds, yet the resulting ac- 
tion of the mechanism is such that at the end of that 
time the weight remains unchanged. 

This fact, the constancy of adult weight, can there- 
fore only be explained by an examination of the action 
of the matter introduced into the interior of the system 
on each other, and an examination of the matter re- 
turned. Whatever is fit for food, when burned in the 
open air, with free access of oxygen, must yield ear- 

What substances may be obtained from petroleum ? Why should 
the weight of an individual change? What is the amount con- 
sumed and secreted in a year ? What is the explanation of con- 
stancy of weight ? 



DIGESTION. 481 

bonic acid, water, and ammonia ; and there are also the 
results of the action of the animal mechanism, as is 
shown by analyzing the excretions. Oxygen, intro- 
duced by the respiratory process through the lungs, ef- 
fects eventually the destruction of the hydrocarbons 
and nitrogenized bodies which have been introduced by 
the digestive apparatus, and carbonic acid, ammonia, and 
the vapor of water, or substances in a transition state, 
which tend eventually to assume those forms, are the 
results. An elevated temperature must also, as a con- 
sequence, be obtained. 

Before the introduction of chemical principles into 
the science of physiology, it w T as a favorite idea that 
the animal system possessed the peculiarity of resisting 
the influence of external agents. This is an error. 
There is no essential difference between the physical 
effects taking place in the body during life and after 
death, nor is there any principle of resistance to exter- 
nal agents possessed by living structures. The only 
distinction' is, that during life the effete materials pass 
off by appointed routes — the kidneys, the lungs, or the 
skin; while after death, these passages being closed, 
they accumulate in the interior of the body. 

The matters returned by an animal to the external 
world are all found to be oxidized bodies, or such as 
arise from processes of oxidation. The result, there- 
fore, is forced upon us that the primitive action of the 
mechanism is the oxidation of the food in the system 
by air which has been introduced by the lungs. 

The process of digestion appears to be exclusively 
for the object of effecting the minute subdivision of the 
food. By the action of the teeth, or other organs of 
mastication, it is first roughly divided, and simultane- 
ously mixed with saliva. It is then passed into the 
stomach, and in that organ mixes with the gastric juice, 
a viscid and acid body. This mixture is perfected by 
certain movements which the food now undergoes, and, 
under the conjoint action of the saliva and the gastric 
juice, it is broken down into a gray, semi-fluid, homo- 

What is the cause of animal heat ? Is an animal emancipated 
from the influence of external agents? What becomes of food in- 
troduced into the body? What is the object of digestion ? What 
fluids act on the food ? 

X 



482 THE NUTRITIVE PROCESSES. 

geneous mass, of the consistency of cream or gruel. A 
part of this, called the CJiyme^ passes out through the 
pyloric orifice of the stomach and enters the intestine, 
and a part is absorbed by the veins of the stomach. 

It has been a question whether artificial digestion 
could be performed, but it now appears to be univer- 
sally admitted that an acidulated water, containing ani- 
mal matter in a state of change, has the power of im- 
pressing analogous changes on organized substances 
submitted to its action, just as the gastric juice, con- 
taining hydrochloric or lactic acid, with pqpsin, an ani- 
mal material undergoing metamorphosis, possesses the 
power of dissolving fibrin or coagulated albumen. 

Soon after its entrance into the intestine, the chyme 
is mixed with bile, pancreatic juice, and the intestinal 
juices, and those parts which have escaped solution 
previously are digested. The valuable portions are 
then absorbed by certain organs in the intestine called 
Lacteals, and thrown into the current of the circulating 
blood. 

Before we can trace the changes which then occur, it 
is proper to remark that, as respects the food itself, it 
may be distinguished into two varieties : 1st. Nitrogen- 
ized food, or that which repairs the tissues ; and-, 2d. 
Calorifacient food, or that used solely to produce heat. 

The nutritive processes of carnivorous animals are 
very simple ; they live on the herbivora, and find in the 
carcasses they consume the fats, the fibrin, and other 
such bodies, which are necessary for their own econo- 
my ; these, therefore, simply require to be brought into 
a state of solution, or of extreme subdivision, and then 
are carried into the blood. In these cases the fats are 
the calorifacient, the muscles, etc., the nitrogenized ele- 
ment. 

But the herbivora find in the vegetable matters they 
use the same essential principles ; their fibrin, albumen, 
and fats are obtained directly from plants in which they 
naturally occur. In the digestive process of the two 
great classes of animals there is not, therefore, in reali- 

What is the chyme ? How may artificial digestion be performed ? 
What is accomplished in the intestine? What varieties of food are 
there ? Why is the digestion of the carnivora simpler than that of 
the herbivora? 



FATS. m 483 

ty, any difference ; both find in their food the elements 
they require. 

The two classes of food are introduced into the sys- 
tem by different routes — the fatty matters passing 
through the lacteals, and the nitrogenized and com- 
pletely dissolved bodies being taken up by the veins of 
the stomach and intestines. 



LECTURE LXXXIX. 

Origin and Destiny of the Fats and Neutral Ni- 
trogenized Bodies. — Fat may be made in the Ani- 
mal System. — Is generally derived directly from the 
Food. — Object of Calorifacient Food. — The Nitro- 
genized Bodies. — Fibrin. — Albumen. — Casein. — 
The Protein Group. — Food is Oxidized in the Body. 

Fats.— Two opinions have been entertained respect- 
ing the origin of the fat which occurs in the adipose 
tissues of animals : 1st. It has been supposed to be pro- 
duced by processes taking effect in the system; or, 2d. 
Simply collected from the food. 

In many various processes fatty bodies arise. Thus, 
when muscular tissue is left in a stream of water, a 
mass of adipocire is eventually found. During the ac- 
tion of nitric acid on fibrin, and in the preparation of 
oxalic acid from starch, oily bodies are produced. If a 
solution of sugar be mixed with powdered chalk, and a 
portion of casein added, on keeping the mixture at 80° 
for some weeks, butyrate of lime is formed, w T ith the ev- 
olution of carbonic acid and hydrogen. 

But, though the power of forming oily from amyla- 
ceous bodies be possessed by the animal mechanism, 
there can be no doubt that it is not resorted to in many 
instances, and that the fats found in the system are di- 
rectly absorbed from the food. Often this absorption 
takes place with so slight a change impressed on the 
oil, that, without difficulty, we can detect its presence 
by the odor or taste. Thus the milk of cows fed on 

How does the food get into the body? What is the origin of the 
fat of animals? How is adipocire produced? When does butyric 
acid arise ? What is the most probable source of fat ? 



484 ORIGIN OF THE FATS. 

linseed cake tastes strongly of that substance; and at 
those seasons of the year when such animals feed on 
young shoots or leaves containing odoriferous oils, as 
the onion, the taste is at once detected in the milk. 

The deposition of fat upon an animal, and the produc- 
tion of butter in its milk, bear a certain relation to the 
amount of oleaginous matter in its food. For this rea- 
son, Indian corn, which contains from eight to twelve 
per cent, of oil, furnishes one of the most valuable arti- 
cles for feeding and fattening cattle. It must be admit- 
ted, however, that where foods without fat are used, 
the system possesses the power of effecting their pro- 
duction ; thus bees will produce wax though fed upon 
pure sugar, and animals will grow fat though eating po- 
tatoes alone. 

The fats which occur in plants pass into the systems 
of graminivorous animals, and there undergo changes, a 
series of partial oxidations occurring. It is only a part 
which is completely destroyed at once, so as to produce 
carbonic acid and water. The residue accumulates in 
the cells of the adipose tissues, to be used at a future 
time; or, if devoured by the carnivorous tribes, is des- 
tined to undergo in them those successive changes which 
bring it back to the condition of carbonic acid and wa- 
ter, and- restore it to the atmosphere, from which it was 
originally derived* by plants. 

The. amylaceous bodies and fats, or the non-nitrogen- 
ized bodies, are the calorifacient food. Their sole office 
is to unite with the oxygen introduced by the lungs, 
and, by the production of carbonic acid and water, keep 
up the temperature of the animal system. 

The principal fatty bodies have already been de- 
scribed, and their general properties indicated. 

Nitrogenized Bodies. — When the expressed juices 
of plants, such as beets, turnips, etc., are allowed to 
stand, there is deposited, after a short time, a coagulum 
or clot, which does not appear to differ in any respect 
from animal Fibrin. If this be removed, and the tem- 
perature of the juice raised to 212°, it becomes turbid 
again, from the deposit of a second body, Albumen. 

Give an instance in the case of the cow. Why is Indian corn val- 
uable for feeding ? What is the destiny of fats ? What do they 
produce ? Describe what occurs on warming a vegetable juice. 



FIBRIN. — ALBUMEN. CASEIN. 485 

On separating this and slowly evaporating, a film forms 
on the surface identical with Casein. These three bod- 
ies contain nitrogen, and may therefore be looked upon 
as the representatives of the neutral nitrogenized class. 

Fibrin may be obtained by beating fresh-drawn blood 
with twigs, and washing with water and ether the 
fibrous filaments which adhere thereto. As thus pre- 
pared, fibrin is whitish, elastic, insoluble in water, al- 
cohol, and ether, but soluble in hydrochloric acid, with 
which it yields a blue solution. It possesses the pow r er 
of decomposing deutoxide of nitrogen, and can coagu- 
late spontaneously. When dried it shrinks very much 
in volume, but recovers its bulk w T hen again moistened. 

Albumen occurs abundantly in the serum of blood 
and tHe white of eggs, from which it may be obtained 
by neutralizing the associated soda with acetic acid. 
On dilution with* cold water it falls as a white precipi- 
tate, soluble in water containing a minute quantity of 
alkali. Exposed to a sufficient heat, albumen coagulates, 
and becomes a wmite^body wholly insoluble in water. 
The strong acids also unite directly with it and form in- 
soluble compounds ; acetic and tribasic phosphoric acids 
are exceptious. With metallic salts, as corrosive subli- 
mate, it gives insoluble precipitates; hence its use as an 
antidote for that poison. 

Casein is found abundantly in milk as cheese. It is 
insoluble in water, but, like albumen, is readily dissolved 
if free alkali be present. It may be obtained by coagu- 
lating milk with sulphuric acid, and dissolving the curd, 
after it has been well washed in water, in a solution of 
carbonate of soda. By standing, it separates into two 
portions, oily and watery. From the latter the casein 
is reprecipitated by sulphuric acid and the process re- 
peated. The casein is finally washed with ether to re- 
move any trace of fat. It is a white substance, soluble 
in an alkaline water, the solution not being coagulated 
by boiling, but a skin forming on the surface as evapo- 
ration goes on. It can, however, be coagulated by cer- 
tain animal substances, as the interior coat of a calf's 
stomach. Casein can dissolve bone-earth. 

The foregoing bodies are sometimes spoken of as the 

What are the properties of fibrin and albumen ? Where is casein 
found ? What are its properties ? 



486 GELATIN. 

Protein group, from the circumstance that they were all 
supposed to be modifications of protein (0 4Q JB 36 O u J)} r 6 ). 
It may be extracted from them by dissolving in an al- 
kaline solution and precipitating with an acid. It is a 
tasteless, white body, soluble in acetic acid and alkalies, 
but insoluble in water. This theory is not, however, 
generally received by chemists, the best authorities re- 
garding the constitution of albumen as (C 216 IT 169 6 q 

Gelatin is obtained by the action of boiling water on 
hide, hoofs, horns, etc. The solution is freed from fat 
by straining and skimming. It forms, on cooling, a soft 
jelly, which contracts as it dries. Solution of gelatin is 
precipitated by corrosive sublimate, tannic acid, or infu- 
sion of galls; with the latter it yields a precipitate 
which is the basis of leather. Glue is an impure, gela- 
tin. 

The nitrogenized bodies introduced into the system 
pass through the same changes as the non-nitrogenized, 
partial oxidations giving rise to various tissue forms, and 
ending in perfect oxidation, with a production of water, 
ammonia, and carbonic acid. 

Whether we regard the heat-making or the nutritive 
food, we see that the result is the same. Introduced 
through the blood-vessels into the system, it is brought 
under the destructive influence of oxygen arriving 
through the lungs ; and, as has been already explained, 
the amount of oxygen is so adjusted to the amount of 
these classes of food combined, that in an adult and 
healthy individual the weight does not change, even aft- 
er the lapse of a considerable period of time. 

Describe the protein theory. How may gelatin be prepared? 
What becomes of the nitrogenized bodies in the system ? How is it 
that the weight of the individual does not change ? . 



CIRCULATION OF THE BLOOD. 487 



LECTURE XC. 

Introduction of Heat-making and Nutritious Food 
into the Blood, and its Transmission through 
the System. — Professor Draper's Explanation of the 
Circulation of the Blood, — Constitution and Proper- 
ties of the Blood. — Plasma and Disks. — Function of 
each. — Coagulation. — Composition of Blood. 

The ordinary principles of capillary attraction are 
amply sufficient to account for the absorption of nutri- 
tious matter from the dige'stive cavities, both by the 
lacteals and the veins. By these it is eventually brought 
into the general current of the circulation, and distrib- 
uted to every part of the system. 

With respect to the forces involved in the circulation 
of the blood, most physiologists have regarded the hy- 
draulic action of the heart as amply sufficient to account 
for all the phenomena. It is now on all hands conceded 
that this organ discharges a subsidiary duty. The 
whole vegetable creation, in which circulatory move- 
ments of liquids are actively carried on without any 
such central mechanism of impulsion — the numberless 
existing acardiac beings belonging to the animal world — 
the accomplishment of the systemic circulation of fishes 
without a heart — and the occurrence in the highest 
tribes, as in man, of special circulations which are iso- 
lated from the greater one, have all served to demon- 
strate that we must look to other principles for the 
cause of these remarkable movements. 

The cause of the circulation of the blood is to be 
found in the chemical relations of that liquid to the tis- 
sues with which it is brought in contact. On the prin- 
ciples of capillary attraction, a liquid will readily flow 
through a porous body for which it has a chemical af- 
finity, but it will refuse to flow through it if it has no 
affinity for it. On this principle we can easily explain 
why the arterial blood presses the venous before it in 

What principle accounts for the absorption of nutritious matter ? 
Does the heart alone carry on the circulation? Give instances to 
show its insufficiency. 



488 



THE BLOOD. 



the systemic circulation, and why the reverse occurs in 
the pulmonary. This explanation of the circulation of 
the blood, which Professor J. W. Draper offered many 
years ago, is now generally admitted to be true. 

The systemic circulation takes place because arterial 
blood has a high affinity for the tissues, and venous blood 
little or none. The pulmonary circulation takes place 
because venous blood has a high affinity for atmospheric 
oxygen, which it finds on the air-cells of the lungs, and 
arterial blood little or none. On the same principle w r e 
may explain the rise of sap in trees, the circulatory 
movements in the different animal tribes, and the minor 
circulations of the human system. 

The most striking peculiarity of the blood is the in- 
cessant change which it undergoes. It is constantly 
being destroyed and as constantly being reproduced. 
It consists of two portions, the Plasma, a clear fluid of 
a yellowish tinge, containing albumen, fibrin, and fat, 
and in it floating disk-like bodies, of different shapes and 
magnitudes in different animals. In man they are cir- 
cular, and about 40 1 oo^ D - of an inch in diameter. In the 
frog they are elliptical, as seen in Fig. 308, about TWir ta 



Flu. 3C: 




of an inch in diameter, and nucleated. They consist of 

What is Dr. Draper's explanation of the circulation ? Why does 
the systemic circulation take place ? Of what portions does the blood 
consist ? Describe a blood disk. 



THE BLOOD. 489 

a cell-wall or sac of a substance like fibrin, containing 
in its interior ffcematiii. When the disks are old and 
about to die, the interior contents change into Hcema- 
pheine, a yellow substance, the coloring matter of the 
urine and bile. 

The disks serve for the carrying of oxygen. They 
absorb it in the air-cells of the lungs, and transmit it to 
all parts of the system. As they grow old and disap- 
pear, new ones are formed from the corpuscles that arise 
from the chyle, a a «, Fig. 308. The plasma serves for 
the purposes of nutrition and for the removal of waste 
bodies. 

Although fibrin exists in plants, it is not absorbed di- 
rectly, but passes through an allied form known as al- 
buminose. Albumen and casein suffer the same modi- 
fication. Besides the direct proof w T e have from the 
analysis of these bodies, we know that fibrin and albu- 
men so closely resemble each other in constitution that 
they are mutually convertible. During the hatching of 
an egg^ from its albumen the flesh (fibrin) of the young 
chicken is formed — a phenomenon accompanying ab- 
sorption of oxygen from the air. In the human system 
abundant observation has proved that there is a direct 
connection between the quantity of oxygen introduced 
through the lungs, and the amount of fibrin in the blood. 
When the respiratory process is unduly active, the disks 
introduce oxygen with rapidity, and the amount of fibrin 
increases ; but when the reverse takes place, the amount 
of fibrin declines. 

The coagulation of the blood is a phenomenon which 
has excited much attention, physiologists generally look- 
ing upon it either as wholly inexplicable, or, what in re- 
ality amounts to the same thing, as due to the death of 
the blood; but it is plain that coagulation would also 
occur during life in the blood were it not for the cir- 
cumstance that the muscles pick out the fibrin and ap- 
propriate it for their repair as fast as it is formed, and 
before it can solidify. The following analysis of blood 
is from Draper's Physiology ; it will serve to give an 
idea of the constitution of that liquid. It must not be 

What is their function ? What body do fibrin, etc., change into ? 
What is the relation of fibrin to albumen ? What is the old and 
what the new hypothesis of coagulation ? 

X2 



490 RESPIRATION. 

forgotten, however, that such analyses, beyond mere gen- 
eral results, are of little value ; the composition of the 
blood varies continually in the same individual: for in- 
stance, the mere accident of his having been thirsty, or 
having recently drank abundantly of water, will make 
an entire change in the analysis of the blood. 

Water... 784.00 

Albumen 70.00 

Eibrin 2.20 

Disks 131.00 

Tats 1.30 

Salts 6.03 * 

Extractive, etc ♦ 5.47 

1000.00 



LECTURE XCI. 

Nature of Respiration and Secretion. — Phenomena 
of Respiration. — Action in the Lungs. — Changes in 
the Blood. — Production of Animal Heat. — Removal 
of Effete Matters. — Composition of Milk. — Its Uses. 

— Chyle. — Lymph. — Mucus. — Pus. — Bile. — Saliva. 

— Gastric Juice. — Urine. — Diabetic and Albuminous 
Urine. — Calculi. — Bone. — Nervous Matter. 

During the starvation of an animal all its various se- 
cretions are still formed, a consideration which proves 
that the production of urine, bile, and other such bodies 
is in reality connected with the destructive processes 
going on in the animal system. These processes of de- 
cay originate in the action of oxygen admitted by the 
process of respiration. 

The lungs, which constitute the organ by which air is 
introduced, are originally developed as diverticula from 
the oesophagus, and finally become an immense congeries 
of cells emptying into the trachea. In respiration they 
are generally passive, the air being introduced and ex- 
pelled alternately by muscular contraction and the prin- 
ciple of the diffusion of gases. It is commonly estimated 
that on an average about seventeen inspirations are 

What is the composition of the blood ? What is the source of the 
secretions? How is this proved? How is air introduced into the 
body ? What is the rate of inspiration and the amount introduced ? 



INTRODUCTION OF OXYGEN. 491 

made each minute, and at each inspiration about seven- 
teen cubic inches of air are introduced. 

The blood presents itself in the air-cells of a deep 
blue color, and is then known as venous blood. Through 
the thin wall of the cell it obtains oxygen from the air 
and gives out carbonic acid. During the act of change 
its tint alters to a bright crimson, and it is now said to 
be arterialized, or to constitute arterial blood. The mag- 
nitude of the scale on which this operation is carried 
forward ma}^ be appreciated from the circumstance that, 
in a man of average size, in a single day about seven 
tons of blood have been exposed to 226 cubic feet of 
air. 

The oxygen thus introduced acts directly either on 
the tissues themselves as it is distributed by the sys- 
temic circulation, or on the calorifacient material con- 
tained in the blood. In the latter case, carbonic acid 
and water are the result ; in the former, carbonic acid, 
water, and ammonia. But these changes can not take 
place without an elevation of temperature. Carbon 
and hydrogen can neither burn in the air nor in the an- 
imal system without evolving heat. The high temper- 
ature which an animal can maintain is therefore directly 
proportional to the quantity of oxygen it consumes. 

The tissues, being thus acted upon, give rise during 
their metamorphoses to new products, which require to 
be removed from the system. These, passing under 
the name of secretions, are discharged by glands or spe- 
cial organs. Thus the carbonic acid, for the most part, 
escapes from the lungs; the ammonia throughthe kid- 
neys ; the water from both these organs and the skin. 
The sulphates and phosphates found in the urine arise 
directly from the sulphur and phosphorus previously ex- 
isting in the muscular fibre and nervous matter. 

As an illustration of the principles here given in rela- 
tion to the functions of nutrition and secretion, the con- 
stitution and properties of milk may be cited. The fol- 
lowing is an analysis of it : 

What change does the blood suffer in the lungs? How much 
blood is aerated in a day? What becomes of the air thus intro- 
duced ? What is the cause of animal heat ? What is the object of 
glands? What is the origin of the sulphates and phosphates found 
in the urine ? 



492 MILK. 

Water .• 873.00 

Casein 48.00 

Sugar of Milk 44.00 

Butter 30.00 

Phosphate of Lime ! 2.30 

Other salts 2.10 

1000.00 

Of the substances here mentioned, all are undoubted- 
ly obtained directly from the food. In the herbage on 
which an herbivorous, milk-giving animal feeds, every 
one of these constituents occur. This has already been 
shown in the case of the fat, sugar, and casein; and the 
evidence is equally complete that all the salts of phos- 
phoric acid and chlorine arise from the same source. 

A young animal, which, in the first periods of its life, 
is nourished exclusively on milk, finds in that milk all 
the various compounds it requires for its own existence 
and growth. The respiratory food is there — it is the 
butter and milk sugar ; the nitrogenized food is there — 
it is the casein ; and we have already seen that albumen 
and casein are both convertible into fibrin. The casein 
thus in the mother's milk becomes converted into flesh 
in the young animal. To insure the growth of its 
bones, phosphate of lime, bone-earth, is present ; there 
is also common salt to form the hydrochloric acid of its 
gastric juice, and to furnish the soda needed in the bile 
and pancreatic juice. 

It remains now to furnish a brief description of the 
properties of the remaining leading animal substances, 
among which may be mentioned the following : 

Chyle is a milky fluid found in the thoracic duct. It 
resembles blood in containing floating cells, and in the 
power of coagulation. It originates from fatty and al- 
buminous matter absorbed by the lacteals. 

Lymph is a fluid found circulating throughout the 
body in the lymphatics. It contains fibrin, which arises 
from waste albuminous matters picked up among the 
tissues. 

Mucus exudes from the surface of mucous mem- 
branes. It is of a white or yellow color, of a viscid 

Give the composition of milk. What is the origin of these con- 
stituents? Why is milk a perfect food? What are the phosphate 
of lime and salt for? Describe chyle, lymph, and mucus. 



ANIMAL FLUIDS. 493 

constitution* and insoluble in water. It dissolves in a 
solution of potassa, and is precipitated by acetic acid 
and alcohol. 

• Pus, a secretion from injured surfaces, resembling 
mucus in many respects, but distinguished by not being 
soluble in potassa solution, but converted by it into a 
gelatinous body, which can be pulled out into threads. 
Examined under the microscope, it contains white, col- 
orless globules. When absorbed into the blood, pus 
appears to act as a powerful poison ; it is a vehicle for 
the most virulent animal poisons, as those of glanders 
and small-pox. 

Bile, a yellow liquid secreted by the liver from the 
portal blood ; it turns green in the air, has a bitter 
taste, and an alkaline reaction, due to the presence of 
soda. It contains glycocholate and taurocholate of so- 
da, cholesterine, fat, mucus, and coloring matter. The 
composition of glycocholic acid is ( C 52 IT i3 12 JV) ; of 
taurocholic acid (C 52 H 45 O u S 2 N'). 

Saliva is a transparent, viscid liquid, secreted in 
glands in the neighborhood of the mouth. It contains 
an organic principle, ptyaline, which acts as a ferment 
to starch and sugar. The tartar which is deposited on 
the teeth consists of salts of the saliva, chiefly phosphate 
of lime, cemented with animal matter. 

Gastric Jtjice is a secretion from the mucous mem- 
brane of the stomach. Its essential ingredients are hy- 
drochloric acid andp _9sm, and its function is to dissolve 
nitrogenized food. 

Urine, a yellow-colored fluid secreted from the kid- 
neys, has an acid reaction; specific gravity, 1.005 to 
1.030; putrefies at a moderate temperature, its urea 
passing into the condition of carbonate of ammonia. 

Composition of Urine. 

Water... 933.00 

Urea 30.10 

Uric Acid 1.00 

Lactic Acid and Extractive 17.14 

Mucus 00.32 

Salts (mostly phosphates and sulphates) 18.44 

1000.00 

Where does pus form? What is bile? Give its composition. 
What is the object of saliva? What is tartar? What is the func- 
tion of gastric juice ? Give the composition of urine. 



494 



SPECIFIC GRAVITY OF URINE. 



The constitution of the urine changes in disease. In 
Diabetes it contains grape sugar, as may be shown by 
adding to a small quantity of it, in a test-tube, a drop 
or two of a solution of sulphate of copper, and its own 
bulk of solution of caustic potassa. A blue liquid re- 
sults, which, on being heated, deposits a green precipi- 
tate, turning red on prolonging the heating, because of 
the formation of suboxide of copper. Diabetic urine 
may even be fermented with yeast, carbonic acid and 
alcohol being produced. 

The specific gravity of diabetic urine is high, as may 
be ascertained by the aid of a urinometer, Fig. 309. 

Fig, 309. 




This consists of a glass bulb, prolonged above and be- 
low into a tube. The lower tube carries a smaller bulb, 
partly filled with mercury, which is intended to act as 
ballast. The upper tube contains a scale divided from 
1000 to 1060, the latter figure being nearest the bulb 
that is lowest. On putting such an instrument into 
distilled water, it should float, as at B, so that the level 
of the liquid is exactly at 1000. If this is not the case, 
it indicates that the instrument-maker has put too much 
or too little quicksilver, as the case may be, in the low- 



How does it change in diabetes ? 
urine ? Describe the urinometer. 



What are the tests for diabetic 



CALCULI. — BONE. — NERVOUS MATTER. 495 

er bulb. On immersing it in a liquid of high specific 
gravity, it floats, as at C ; while in diabetic urine the 
liquid stands at some intermediate point, as seen at A. 

Albumen is found in urine in Bright's disease, and 
may be detected by heating. A white precipitate forms, 
insoluble in nitric acid. The precipitate of phosphates 
formed by heating is soluble in that acid. Urine may 
also contain blood, pus, casts of the uriniferous tubuli, 
etc., and must in such cases be subjected to microscopic 
examination. 

Urinary Calculi are stony concretions formed in 
the bladder of man and many animals. They are of 
different kinds: 1st. Uric acid; 2d. Urate of ammonia; 
3d. Phosphate of lime, magnesia, and ammonia; 4th. 
Oxalate of lime, or mulberry calculus ; 5th. Cystic and 
xanthic oxides. 

Bones consist of two parts, an animal and an earthy 
matter. The former is gelatin, the latter phosphate of 
lime (bone-earth). 

Nervous Matter consists of an albuminous sub- 
stance, with several fatty principles, distinguished by 
the remarkable fact that they contain phosphorus, which 
oxidizes when they are in action. 

As it would not, however, be consistent with the plan 
of this book to prolong the consideration of this subject, 
and become involved in physiological questions, the 
reader is referred for farther information to Draper's 
Physiology, where such matters are fully discussed. 

When is albumen found in urine ? How is it detected ? What is 
the composition of urinary calculi? What is the composition of 
bone ? What is the peculiarity of nervous matter ? 



INDEX. 



Absolute alcohol, 407. 
Acetal, 419. 
Acetification, 419. 
Acetone, 422. 
Acetyle compounds, 417. 
Acid, acetic, 419. 

" aconitic or equisetic, 455. 

" aldehydic,418; 

u - alloxanic, 451. 

" althionic, 417. 

" amygdalic, 443. 

" anilic or indigotic, 467. 

" anthr anilic, 467. 

" antimonic, 361. 

" antimonious, 361. 

" apocrenic, 470. 

" apoglucic, 398. 

" arsenic, 359. 

" arsenious, 356. 

" " tests for, 356. 

" benzoic, 432. 

" boheic, 457. 

" boracic, 302. 

" butyric, 473. 

" caffeotannic, 457. 

" capric and caproic, 473. 

" carbazotic, 467. 

" carbolic, 478. 

" carbonic, 295. 

u " liquefaction of, 

297. 

11 chloracetic, 422. J 

" chloric, 282. 

" chlorous, 282. 

" chlorovalerisic, 433. 

" chromic, 352. 

" chrysammic, 468. 

" chrysanilic, 467. 

" cincbonic, 461. 

" cinnamic, 439. 

" citric, 455. 

" comenic, 460. 

" crenic, 478. 

" croconic, 400. 



Acid, cyanic, 444. 

" cyan uric, 444. 

" elaidic, 472. 

" ellagic, 458. 

" ethalic, 473. 

" ethionic, 417. 

" ferric, 344. 

" fluoboric, 303. 

" fluosilicic, 304. 

" formic, 428. 

" fulminic, 444. 

" fumaric, 456. 

" gallic, 372. 

" geic, 478. 

" glucic, 398. 

" hippuric, 436. 

" humic, 478. 

" hydriodic, 288. 

" hydrobromic, 290. 

<j hydrochloric, 283. 

" hydrocyanic, 441. 

" hydroferrocyanic, 446. 

" hydrofluoric, 291. 

" hydrofluosilicic, 305. 

" hydromellonic, 449. 

" hydrosulphocyanic, 448 a 

" hydros ulph uric, 271. 

" hypochloric, 282. 

" hypochlorous, 281. 

" hyponitrous, 261. 

" hypophosphorous, 275. 

" hyposulphurous, 271. 

" igasuric, 462. 

" isatinic, 467. 

" isethionic, 417. 

" japonic, 457. 

" kakodvlic, 425. 

" kinic, 461. 

" lactic, 409. 

" lithic, 450. 

" maleic, 456. 

" malic, 456. 

" manganic, 338. 

" margaric, 470. 

" meconic, 460. 



498 



INDEX. 



Acid, melanic, 438. 

" melasinic, 398. 

" mesoxalic, 451. 

" metagallic, 458. 

" metaphosphoric, 276. 

" methionic, 417. 

" mucic, 401. 

" muriatic, 283. 

" mykomelinic, 451. 

" myristic, 472. 

" nitric, 263. 

" nitrohydro chloric, 286. 

" nitrous, 261. 

" cenanthic, 413. 

" oleic, 471. 

" oxalic, 398. 

" oxalhydric, 400. 

" oxaluric, 451. 

" palmitic, 472. 

" parabanic, 451. 

" paramaleic, 456. 

" paratartaric, 454. 

" pectic, 396. 

" perchloric, 283. 

" permanganic, 339. 

" phenylic, 478. 

" phosphogly eerie, 472. 

" phosphoric, 276. 

" phosphorous, 275. 

" phosphovinic, 414. 

" picric or carbazotic, 467. 

" pinic, sylvic, and pimaric, 

475. 

" propionic, 472. 

" prussic, 441. 

cc purpuric, 452. 

" pyrogallic, 458. 

" pyroligneous, 419. 

" pvromeconic, 461. 

i; pyrophosphoric, 276. 

" pyrotartaric, 455. 

" racemic, 454. 

" rhodizonic. 400. 

61 rubinic, 457. 

" saccharic, 400. 

il sacehulmic, 398. 

" salicylic, 437. 

" sebacic, 472. 

" silicic, 303. 

" stearic, 470. 

tc suberic, 472. 

" succinic, 472. 

" sulphacetic, 422. 



Acid, sulphamylic, 432. 

" sulphindigotic, 467. 

" sulphobenzoic, 434. 

" sulphocyanic, 448; 

" sulphogiy eerie, 472. 

" sulphomethylic, 428. 

" sulphomephalic, 477. 

li sulphosaccharic, 397. 

" sulphovinic, 413. 

li sulphuric, 269. 

" sulphurous, 267. 

11 tannic, 456. 

" tartaric, 453. 

" thionuric, 452. 

" ulmic, 397, 478. 

ift uramilic, 452. 

" uric, 4o0. 

" valerianic, 432. 

". valeric, 431. 

" xanthic, 424. 
Acids, coupled, 455. 
Aconitine, 462. 
Adipocire, 433. 
Affinity, chemical, 212. 
Air-pump, 246. 
Albumen, 485. 

" vegetable, 484. 
Albuminose, 489. 
Alcargen, 425. 
Alchemy, 1. 
Alcohol, 407. 
Aldehyde, 418. 
Alkaloids, 458. 
Alkarsine, 425. 
Allantoin, 450. 
Allotropism, 211. 
Alloxan, 451. 
Alloxantine, 451. . 
Alumina, 333. 

" sulphates, 335. 
Aluminum, 332. 
Alums, 335. 

Amalgamation process, 373. 
Amalgams, 373. 
Amber, 475. 
Amidine, 392. 
Amidogen, 305. 
Ammelin and ammelid, 448. 
Ammonia, carbonate, 440. 
" nitrate, 440. 
" preparation and prop- 
erties of, 306. 
" sulphate, 440. 



INDEX. 



499 



Ammoniacal amalgam, 307, 440. 
Ammonium, 307, 440. 

" chloride, 440. 

" sulphide, 441. 

Amygdaline, 442. 
Amyle compounds, 430. 
Amylene, 432. 
Amylum, 391. 
Anesthetic, 410, 429. 
Anatto, 466. 
Aneroid barometer, 255. 
Aniline, 463. 
Animal chemistry, 480. 
Antearine, 462. 
Anthracite, 479. 
Antimony, 360. 

" chloride, 361. 

" oxide, 361. 

" sulphides, 361. 
Antozone, 229. 
Aqua regia, 2S6. 
Arabine, 396. 
Arc, Voltaic, 156. 
Argol, 408. 
Aricine, 461. 
Arrow-root, 392. 
Arsenic, 355. 

" sulpirides, 360. 
Arterialization, 491. 
Asphaltum, 479. 

Atmosphere, composition of, 242. 
' ; physical constitution 

of, 244. 
Atmospheric pressure, 245. 
Atomic weights, 193. 

" theory, 4. 
Atoms, 4. 
Atropine, 462. 
Attraction, 126. 
Aurum musivum, 351. 
Azote, 241. 

B. 

Balloon, 16. 
Balsam, 476. 
Barium, 324. 

" chloride, 325. 

" oxides, 325. 

" sulphide, 325. 
Barley sugar, 393. 
Barometer, 253. 
Baryta, 325. 

" carbonate, 326. 



Baryta, sulphate, 326. 
Basil Valentine, 2, 
Bassorine, 396. 
Battery, electrical, 137. 

" Voltaic, 151. 
Bell metal, 364. 
Benzamide, 434. 
Benzine, 435, 480. 
Benzoine, 435. 
Benzone, 435. 
Benzoyle compounds, 433. 
Bezoars, Oriental, 458. 
Bile, 493. 
Biscuit-ware, 334. 
Binary hypothesis, 125. 
Bismuth," 367. 

" nitrate, 367. 

" oxides, 367. 
Bitumen, 479. 
Bleaching powder, 330. 
Blood, composition of, 490. 
Boiling points of fluids, 45, 56. 
Bone-earth, 330. 
Bones, composition of, 495. 
Boron, 301. 

" nitride, 302. 
Bouquet of wine, 406. 
Brass, 364. 

Breguet's thermometer, 30. 
Bright's disease, 495. 
British gum, 393. 
Bromine, preparation and prop- 
erties o£, 289. 
Brucia, 462. 
Brush, electrical, 137. 
Burning-glass, 92. 
Bunsen's battery, 155. 
Butyrine, 478. 



Cadmium, 349. 

" compounds of, 349. 
Caesium, 96, 323. 
Caffeine, 462. 
Calcium, 327. 

" chloride, 328. 

" fluoride, 328. 

" sulphide, 328. 
Calculi, urinary, 495. 
Calomel, 372. 
Calorimeter, 32. 
Calorimotor, 164. 
Camphor, 474. 



500 



INDEX. 



Camphor, artificial, 474. 
Candle-bomb, 50. 
Caoutchouc, 475. 
Capacity for heat, 31. 
Caproine, 472. 
Caramel, 394. 
Carbon, 291. 

" chlorides, 41G. 

" compounds with oxygen, 
293. 

" sulphide, 300. 
Carbonic oxide, preparation and 

properties of, 294. 
Carbyle, sulphate of, 417. 
Carmine, 468. 
Carthamine, 466. 
Casein, 485. 

" vegetable, 485. 
Cassava, 392. 
Cast iron, 341. 
Catalysis, 217. 
Catechin and Catechu, 457. 
Cedriret, 477. 
Cellulose, 396. 
Cerine, 473. 
Cerium, 336. 
Chameleon mineral, 339. 
Charcoal, properties of, 293. 
Chemistry, history of, 1. 
Chloral, 423. 
Chloric acid, 282. 
Chlorine, 278. 

" compounds with oxy- 
gen, 281. 

" preparation and proper- 
ties of, 278. 
Chlorisatine, 467. 
Chlorobenzide, 436. 
Chlorocinnose, 355. 
Chloroform, 429. 
Chlorophyll, 468. 
Chlorosamide, 438. 
Chlorous acid, 282. 
Chlorureted acetic ether, 423. 
" formic ether, 423. 

Chrome yellow, 353. 
Chromic acid, salts of, 353. 
Chromium, 351. 

" oxide, 351. 

Chyle, 492. 
Chyme, 482. 
Cinchonia, 461. 
Cinnabar, 372. 



Cinnamyle compounds, 438. 

Circle, Voltaic, 148. 

Circulation of blood, 487. 

Clay, 338. 

Clay iron-stone, 340. 

Coagulation, 489. 

Coal, 479. 

" oil, 477. 
Cobalt, 347. 

" character of salts of, 347. 

" chloride, 347. 

" oxalate, 347. 

" oxides, 347. 
Cobaltocyanogen, 448. 
Cocoa tallow, 472. 
Codeia,460. 
Cohesion, 6. 
Colchicine, 462. 
Cold rays, 79. 
Collodion, 121, 401. 
Colloid, 390. 
Colophony, 375. 
Coloring principles, 465. 
Colors, 103. 
Columbium, 354. 
Combination by volumes, 202. 

" laws of, 199. 

Combining numbers, 193. 
Combustion, 383. 

" furnace, 326. 

" tube, 385. 

Compound bar, 28. 

" radicals, 379. 

Condensation of gases, 52. 
" of vapors, 54. 

Conduction, 68, 125. 

" in crystals, 72. 

Congress Spring, 240. 
Conine or Conia, 463. 
Conservation of force, 9. 
Copper, 363. 

" alloys of, 364. 

" arsenite, 364. 

" carbonates, 364. 

u nitrate, 364. 

" oxides, 363. 

" sulphate, 364. 
Correlation of force, 9. 
Corrosive sublimate, 372. 
Creasote, 477. 
Crown of cups, 151. 
Cruickshank's battery, 151. 
Cryophorus, 60. 



INDEX. 



501 



Crystallization, Crystallography, 

204. 
Crystalloid, 390. 
Culinary paradox, 56. 
Cnpellation, 368. 
Cyanogen, 300, 441. 

" chlorides of, 446. 

Cystic oxide, 453. 

D. 

Daguerreotype, 120. 
Dalton's theory, 4. 
Dammara resin, 475. 
Daniell's battery, 152. 
Daphnine, 462. 
Daturine, 462. 
Davy's theory, 3. 
Decomposition of water, 156. 
Delphinine, 462. 
Deutoxide of nitrogen, 260. 
Developers, 123, 420. 
Dew, 85. 
Dew point, 63. 
Dextrine, 392. 
Diabetes, 494. 
Dialysis, 390. 
Diamagnetism, 176. 
Diamond, 291. 

" phosphorescence of, 
115. 
Dianium, 337. 
Diastase, 392. 
Diathermacy, 81. 
*Dicyanomelaniline, 383. 
Didymium, 337. 
Dielectrics, 142. 
Differential thermometer, 18. 
Diffusion of gases, 255. 

" of liquids, 390. 
Digestion, 481. 
Dimorphism, 209. 
Disks, 487. 
Dispersion, 93. 
Dragon's blood, 475. 
Draper's photometer, 91. 

" researches on light, 111. 

" " on thermo- 

electricity, 186. 
Drummond light, 224. 
Dufay's theory, 136. 
Dutch liquid, 415. 



E. 

Earthenware, manufacture of, 334. 
Ebonite, 475. 
Ebullition, 53. 
Elaidine, 472. 
Elaldehyde, 418. 
Elaterine, 462. 

Electricity, action of on magnet, 
172. 

" animal, 188. 

" conduction of, 125. 

" of steam, 146. 

V statical, 124. 

" Voltaic, 147. 
Electro-chemistry, 160. 
Electrolysis, 162. 
Electrometers, 140. 
Electrotype, 162. 
Etectrophorus, 146. 
Emetine, 462. 
Emulsine, 443. 
Equivalent numbers, 198. 

table of, 193. 
Eremacausis, 383. 
Essences, 473. 
Ethal, 478. 
Ether, 409. 
t( continuous process for, 415. 
" hydrochloric, 411, 423. 
Ethers, compound, 411. 
Etherine and Etherole, 416. 
Ethyle group, 411 
Endiometer, 243. 
Eupion, 476. 
Evaporation, 66. 

" at low temperature, 

59. 

" conditions of, 67. 

Expansion of solids, 27. 

" of fluids, 19. 

" of gases, 15. 

F. 

Faraday's theory of polarization, 

142. 
Fatty bodies, 469, 483. 
Fermentation, acetous, 405. 

" alcoholic, 383, 403. 

« lactic, 404, 409. 

Ferricyanogen compounds, 447. 
Ferrocyanogcn compounds, 446. 
Fibrin, 485. 



502 



INDEX. 



Fibrin, vegetable, 484. 

Fire syringe, 37. 

Fixed air, 219. 

Flame, structure of, 70, 113, 227. 

Fluoride of boron, 303. 

Fluorine*, 290. 

Foot-pound, 11. 

Formomethyial, 492. 

Franklin's theory, 135. 

Freezing mixtures, 43. 

' ; of water by evaporation, 
61. 
Fusel oil, 431. 
Fusible metal, 29, 367. 

G. 

Galvanism, 147. 
Galvanometer, 187. 
Gamboge, 466, 475. 
Gasometer, 220. 
Gastric juice, 493. 
Geber, 2. 

Geissler's tubes, 183. 
Gelatin, 486. 
Gelose, 396. 
Gentianine, 462. 
Geoffroy's tables, 3, 215. 
Glass, manufacture of, 334. 

" soluble, 335. 
Glucinum, 335. 
Glucose, 395. 
Glycerine, 472. 
Gold, 373. 

" compounds of, 373. 
Goniometers, 208. 
Goulard's water, 421. 
Graphite, 292. 

Gravity, specific, of gases, 249. 
Green, Scheele's, 356. 
Grouping, 196. 
Grove's batteiy, 154. 
Gum, Arabic, 396. 

" British, 393. 

" tragacanth, 396. 
Gun-cotton, 401. 
Gunpowder, 318. 
Gutta perch a, 476. 
Gypsum, 329. 

H. 

Haemaphein, 489. 
Hamiatin, 489. 
Haematite, 340. 



Haamatoxyline, 466. 
Haloid salts, 195. 
Hare's blowpipe, 233. 
Heat affects measures, 13. 
" animal, 481. 
" capacity for, 31. 
" conduction of, 68. 
" dynamic theory of, 11. 
" exchanges of, 83. 
" expansion by, 12. 
" latent, 39. 

" produced by electricity, 145. 
" " friction, 9. 

" radiation, reflection, absorp- 
tion, and transmission of, 
76. 
" varieties, of, 80. 
Hesperidine, 462. 
Homologous series, 381. 
Hydrobenzamide, 434. 
Hydrogen, antimoniureted, 362. 
" arseniureted, 360. 
" light carbureted, 298. 
" peroxide of, 240. 
" persulphide of, 273. 
" phosphureted, 277. 
" preparation and prop- 
erties of, 229. 
" sulphureted, 271. 

Hygrometer, Darnell's, 63. 
" Saussure's, 62. 

" wet bulb, 64. 

Hygrometry, 52. 
Hyoscyamine, 462. 
Hyponitrous acid, 261. 
Hyposulphurous acid, 271. 



Ice, 241. 
Ilmenium, 354. 
Inca Indians, 17. 
Indestructibility of matter, 9. 
India-rubber, 475. 
Indigo, 466. 
Indium, 337. 
Induction, 129. 
Interference, 103. 
Interstices, 4. 
Inuline, 392. 

Iodine, preparation and proper- 
ties of, 286. 
Iridium, 375. 
Iron, 340. 



INDEX. 



503 



Iron, carbonate, 345. 

" cast, varieties of, 341. 

" characters of salts of, 344. 

" chlorides, 345. 

" manufacture, 340. 

" oxides of, 343. 

" passive, 342. 

" sulphates, 345. 

" sulphides, 345. 
Isatine, 467. 
Isomerism, 211. 
Isomorphism, 210. 

K. 

Kakodyle and it's compounds, 424. 

Kakoplatyle, 465. 

Kapnomar, 477. 

Kermes mineral, 362. 

Kerosene, 480. 

Koumiss, 395. 

Kyanol, 463. 



Lac, 475. 
Lacteals, 482. 
Lactine, 395. 
Lampblack, 292. 
Lamp, safety, 71. 
Lanthanum, 336. 
Latent heat, 39. 
Laughing-gas, 259. 
Laws of combination, 199. 
Lead, 365. 

" action of water on, 365. 

" alloys of, 367. 

" carbonate, 366. 

" characters of salts of, 366. 

" chloride, 366. 

" iodide, 366. 

" nitrate, 367. 

" oxides, 366. 
Leaven, 403. 
Lecanorine, 462. 
Leiocome, 393. 
Leukol, 464. 
Leydenjar, 136. 
Light, cause of, 87. 

" chemical action of, 116. 

" reflection, refraction, and 
polarization of, 108, 111. 

" wave theory of, 100. 
Lignine, 396. 
Lignite, 479. 



Lime, 327. 

" carbonate, 329. 

" chloride, 330. 

" oxalate, 400. 

" phosphate, 330. 

" salts, characters of, 328. 

" sulphate, 329. 
Liquor of Libavius, 351. 
Lithium, 323. 
Litmus, 467. 

Liquids, expansion of, 19. 
" conduction of, 73. 
Lunar photography, 116. 
Lymph, 492. 

M. 

Machines, electrical, 127. 

Madder, 455. 

Magdeburg hemispheres, 248. 

Magenta, 464. 

Magnesia, 331. 

" carbonate, 331. 

" characters of salts of, 
331. 

" phosphate, 332. 

" sulphate, 332. 
Magnesium, preparation and prop- 
erties of, 330. 
Magnetic field, 177. 
Magnetism, 168. 
Magnets, artificial, 168. 
Magneto-electricity, 180. 
Malachite, 364. 

Manganese, characters of salts of, 
339. 

" chloride, 339. 

" oxides, 338. 

1 i preparation and prop- 

erties of, 338. 

" sulphate, 340. 

Marcet's boiler, 52. 
Margarine, 470,471. 
Margarone, 471. 
Marine glue, 476. 
Marriotte's law, 50, 257. 
Marsh's test for arsenic, 358. 
Mauve, 463. 
Maximum density, 24. 
Meconine, 462. 
Medicated tubes, 132. 

" waters, 473. 
Melam and melamine, 448. 
Mellone. 449. 



504 



INDEX. 



Melting points, 39. 
Mercaptan, 412, 430. 
Mercury, 371. 

" characters of salts of, 
372. 

" chlorides, 372. 

" iodides, 372. 

" nitrates, 372. 

" oxides, 371. 

" sulphates, 372. 

" sulphides, 372. 
Mesityle, 423.- 
Metaldehyde, 418. 
Metal, fusible, 29, 367. 
Metals, general properties of, 309. 

" classification of, 310. 
Methyle compounds, 426. 
Methylethylamylophenylium, 383. 
Microcosmic salt, 322. 
Milk, composition of, 492. 
Mindererus spirit, 42 1 . 
Mineral chameleon, 339. 

" waters, 239. 
Moire metallique, 351. 
Molybdenum, 354. 
Moon photographed, 116. 
Moore's test, 398. 
Mordants, 465. 
Morphia, 459. 
Morse's telegraph, 175. 
Mosaic gold, 251. 
Mucilage, 396. 
Mucus, 492. 
Multipliers, 173. 
Merexan, 452. 
Murexide, 452. 
Muscovado sugar, 393. 
Myricine, 473. 

N. 

Naphtha, 477. 
Naphthaline, 477. 
Narceia, 460. 
Narcotina, 460. 
Negative, 121. 
Nervous substance, 495. 
Nickel, 346. 

" sulphate, 346. 
Nicotine, 462. 
Nihil album, 348. 
Niobium, 354. 
Nitric acid, 263. 

" discovery of, 2. 



Nitrobenzide, 436. 
Nitrogen, chloride, 283. 

" compounds with oxy- 
gen, 258. 
" determination of, 388. 
* ' preparation and proper- 
ties of, 241. 
Nitrous acid, 261. 

" oxide, 258. 
Nomenclature, 8, 191. 
Norium, 354. 
Nutmeg butter, 472. 
Nutrition, function of, 481. 

O. 

CEnanthic ether, 413. 

Ohm's theory, 165. 

Oil of bitter almonds, 433. 

" cajeput, 473. 

" cinnamon, 473. 

" copaiva, 473." 

" horseradish, 473. 

" lavender, 473. 

" lemons, 473. 

" mustard, 473. 

y peppermint, 473. 

" rosemary, 473. 

" spiraea, 437. 

" storax, 473. 

" turpentine, 474. 

" vitriol, preparation of, 269. 

" wine, heavy, 415. 
Oils and fats, 469. 
" palm and cocoa, 472. 
" volatile, 473. 
Olefiant gas, 299. 
Oleine, 471. 

Orceine and orcine, 468. 
Organic bodies, analysis of, 324. 

" " classification of, 

383. 

" " decomposition of 

by heat, 382. 

" " general charac- 

ters of, 377. 

" chemistry, 377. 
Orpiment, 360. 
Osmium, 376. 
Oxalates, 399. 
Oxamethane, 412. 
Oxamide, 412. 

Oxygen, preparation and proper- 
ties of, 212. 



INDEX. 



505 



Oxvhydrogen blowpipe, 233. 
Ozone, 228. 



Palladium, 373. 
Palmitine, 472. 
Palm oil, 472. 
Papin's digester, 54. 
Paracyanogen, 441. 
Paraffine, 476, 480. 
Par anaphth aline, 477. 
Parchment paper, 397. 
Pascal's experiment, 254. 
Pectine, 396. 
Pelopium, 354. 
Perchloric acid, 283. 
Petroleum, 479. 
Pewter, 351. 
Phene, 435. 
Phlogistic theory, 7. 
Phloridzine, 462. 
Phosphorescence, 114. 
Phosphori, 114. 
Phosphoric acid, 276. 
Phosphorus compounds with oxy- 
gen, 275. 

" preparation and prop- 

erties of, 273. 
Phosphureted hydrogen, 277. 
Photography, 119. 
Photometers, 89. 
Picamar, 477. 
Picrotoxine, 462. 
Pile, Voltaic, 151. 
Piperine, 462. 
Pitch, 476. 
Pit coal, 479. 
Pittacal, 477. 
Plasma, 487. 
Platinum, 374. 

" black, 375. 

chloride, 375. 

" oxides, 375. 

" power of determining 
union of gases, 374. 
spongy, 374. 
Plumbago or graphite, 292. 
Pneumatic trough, 219. 
Polarization of light, 108, 394. 

" of heat, 86. 

Populinc, 462. 

Porcelain, manufacture of, 334. 
Positive, 121. 



Potassa, 315. 

" bicarbonate, 317. 

" • bisulphate, 317. 

" carbonate, 317. 

" chlorate, 318. 

" hydrate of, 315. 

" nitrate, 318. 

" oxalate, 399. 

" salts, tests for, 316. 

" sulphate, 317. 
Potassium, chloride of, 317. 
w iodide of, 317. 

peroxide of, 316. 
" preparation and prop- 
erties of, 313. 
" sulphides of, 316. 
Potato oil and its compounds, 431. 
Printers' ink, 469. 
Prism, 93. 
Protein, 486. 
Prussian blue, 447. 
Pulse glass, 61. 
Purple of Cassius, 373. 
Pus, 493. 

Putty powder, 350. 
Pyroacetic spirit, 422. 
Pyrometer, 26. 

Daniell's, 30. 
Pyroxylic spirit, 427. 
Pyroxyline, 401. 

Q. 

Quartation, 373. 
Quercitron bark, 466. 
Quicksilver, 371. 
Quinia, 461. 
Quinoidine, 461 . 
Quinoline, 464. 

Pv. 

Radiation, 76. 

" interstitial, 12, 68; 
Raphides, 400. 

Rays of the sun, chemical, 118, 
Realgar, 360. 
Reflection, law of, 110. 
Refraction, law of, 110. 
Regelation, 44. 
Reinsch's test, 357. 
Repulsion, 126. 
Resins, 476. 
Respiration, 261, 490. 
Rheostat, 167. 



506 



INDEX. 



Rhodium, 375. 
Rochelle salts, 454. 
Rouge, 466. 
Rubidium, 96, 324. 
Rudberg's law, 15. 
Ruhnikorff's coil, 181. 
Rupert's drops, 29. 
Ruthenium, 376. 

S. 
Sacchulmine, 398. 
Safety-jet, Hemming's, 71. 
Safetv-lamp, 71. 
Sago" 392. 
Salicine, 437. 
Salicyle compounds, 437. 
Saliva, 493. 

Sanctorio's thermometer, 16. 
Seheele's green, 356. 
Secretion, 490. 
Seignette salts, 454. 
Selenium, 273. 
Silicon, 303. 
Silver, 367. 

" ammoniuret, 370. 

" characters of salts of, 369. 

" chloride, 369. 

" German, 346. 

" iodide, 369. 

" nitrate, 369. 

" oxides, 369. 

< ; plating, 163. 

" sulphide, 369. 
Silvering on glass, 370. 
Smalt, 347. 
Smee's battery, 153. 
Snow ciwstals, 236. 
Soaps; saponification, 470. 
Soda, biborate, 323. 

" bicarbonate, 321. 

" carbonate, 321. 

" hydrate, 320. 

" nitrate, 322. 

" phosphates of, 322. 

" sulphate, 42, 321. 

" water, 296. 
Sodium, chloride, 320. 

" prepartion and proper- 
ties of, 319. 
Solanine, 462. 
Solder, 351. 
Spark, 145. 
Specific gravity, 203. 



Specific heat, 31. 

" induction, 144. 
Spectra, 98. 
Spectres, 117. 
Spectroscope, 97. 
Spectrum, solar, 93. 
Speculum, metal, 364. 
Spermaceti, 473. 
Spheroidal state of water, 57. 
Spiraea ulmaria, oil of, 437. 
Spirit of wine, 40S. 
Starch, 391. 
Steam, elastic force of, 58. 

" engine, 55, 66. 
Stearine, 470. 
Stearopten, 474. 
Steel, 342. 

Stone-ware, manufacture of, 334. 
Strontia, 326. 

" nitrate, 327. 
" sulphate,. 32 7. 
Strontium, 326. 
Strychnia, 462. 
Sublimate, corrosive, 372. 
Substitution, 380. 
Sucrose, 393. 
Sugar, cane, 393. 

" eucalyptus, 396. 

" from ergot of rye, 396. 

" grape, 395. 

" of lead, 421. 

" of milk, 395. 
Sulphobenzide, 436. 
Sulphocyanogen compounds, 448. 
Sulphur compounds with oxygen, 

267. 
" occurrence in nature, 

265. 
" properties of, 261. 
Sulphureted hydrogen, 271. 
Sulphuric acid, 269. 
Sulphurous acid, 267. 
Sun, atmosphere of the, 95. 
Symbols, 195. 

table of, 193. 
Sympathetic ink, 347. 
Synaptase, 443. 
System, crystallograpbical, 204. 

T. 

Tapioca, 392. 

Tar, varieties of, 476. 

Tartar, cream of, 454. 



INDEX. 



507 



Tartar emetic, 454. 
Telescope, silvered-glass, 116. 
Tellurium, 362. 
Thallium, 337. 
Thebaia, 460. 
Theine, 462. 
Theobromine, 462. 
Thermo-electricity, 183. 
Thermo-electric pile, 82. 
Thermometer, Breguet, 30. 

' ' construction of, 20. 

" differential, 18. 

"' Sanctorio's, 16. 

" scales, 21. 

Thorium, 336. 
Tin, 349. 
" chloride, 350. 
" oxide, 350. 
" sulphide, 351. 
Tin plate, 351. 
Titanium, 355. 
Toning, 122. ' 
Torpedo, 188. 
Torula, 403. 
Trade-winds, 75. 
Transverse vibrations, 102. 
Tungsten, 354. 
Turmeric, 466. 
Turpeth mineral, 372. 
Type metal, 362. 
Types, chemical, 379. 

U. 

Ulmine, 397, 478. 
Undulatory theory, 100. 
Uramile, 452. 
Uranium, 354. 
Urea, 445, 449. 
Urinary calculi, 495. 
Urine, composition of, 493. 
Urinometer, 494. 

V. 

Vanadium, 353. 
,i Vapor, elastic force of, 50, 58. 
Vapors, density of, 66. 



Vapors, nature of, 46. 
Vaporization at low temperature, 

laws of, 47. 
Varrentrapp and Will's bulbs, 389. 
Veratrine, 462. 
Verdigris, 421. 
Vermilion, 372. 
Vinegar, 419. 
Vitriol, blue, 364. 

" green, 345. 

" oil of, 269. 

" white, 345. 
Voltameter, 164. 
Volumes, combination by, 202. 
Vulcanization, 475. 

W. 

Water, composition of, 156, 234. 

" of crystallization, 239. 
Wave% length of, 107. 
Wax, 473. 
Wines, 406. 
Wire gauze, 70. 
Wood ether, 426. 

" spirit and its compounds, 
426. 
Woody fibre, 396. 

X. 

Xanthic acid, 424. 

" oxide, 452. 
Xanthophylline, 468. 
Xyloidine, 401. 



Y. 



Yeast, 403. 
Yttrium, 336. 



Z. 



Zaffre, 34?. 
Zamboni's piles, 142. 
Zinc, 347. 

" oxide, 348. 

" silicate, 348. 

" sulphate, 348, 
Zirconium, 335, 



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